COMB YOUR SLEEPY HEAD= to encourage your sleepy boy, who just got up, to comb his head (tidy their hair using a comb: see picture).
Here, when we say “sleepy head” instead of “sleepy child” we’re using a common rhetoric device called metonymy, which is defined as “a figure of speech that consists of the use of the name of one object or concept for that of another to which it is related, or of which it is a part, as “sceptre” for “sovereignty,” or “the bottle” for “strong drink,” or “count heads (or noses)” for “count people.” “

GRAB= (coll.) take.

YOU GOTTA= (coll.) You’ve got to, you must.

ORTHODONTIST= Dentist, tooth doctor.

DON’T SHOVEL= Don’t eat so much so fast.
A shovel /ʃʌvəl/ is a tool for moving earth (see picture), and kids sometimes use their spoon like a shovel to put big amounts of food into his mouth quickly, or simply quickly, even if it’s small quantities at a time, and that reminds us of a worker shovelling sand.

PLAY ROUGH /rʌf/= Be a brute playing (when two little boys play rough, quite often, sooner or later, one ends up crying)

PLAY FAIR= Play according to the rules, in a civilized manner, without cheating or abusing in any way.

WORK IT OUT= Solve it.

TAKE A DARE= Accept a dare. A dare is when somebody dares you to do something difficult or dangerous. If they say “I dare you to climb that tree”, they mean that you should prove you can do it, or else, you will prove to be a coward or unfit. Daring others is a common thing especially among boys.

GET ALONG= Have a good relationship with somebody else.

PUT YOUR STUFF AWAY=  Your stuff is your things, and to put something away is to remove them from where they are and, hopefully, put them back in its place.

DO WE HAVE ALL DAY?= A common expression (especially from someone in authority) to show impatience because they’ve been waiting for too long or they fear they’ll have to be waiting for too long, so implicitly the question means "I don't have all day for waiting".

WERE YOU BORN IN A BARN? WOULD YOU LIKE SOME HAY?= A BARN is a wooden building on a farm used to keep hay, tools and maybe some animals (see picture).  HAY is straw used for feeding animals. The question “were you born in a barn?” is commonly used as an ironic rhetoric question when someone has no manners, is not polite (it’s comparing you with farm animals). And the second question “would you like some hay” is sometimes added to give even more emphasis to the comparison (animals eat hay, so if you look like an animal maybe you’d like to eat some hay)

GET OFF THE PHONE= Stop talking on the phone.

TURN IT DOWN= Reduce the volume (of the TV or the music).

TEXTING AT THE TABLE= Texting is writing text messages on the phone (sms). If you do something "at the table", you do it when you are sitting at the table to eat (lunch, dinner...)

WITH WHOM= After prepositions we shouldn’t use WHO, but WHOM.

SAYING THANK YOU, PLEASE, EXCUSE ME, MAKES YOU WELCOME EVERYWHERE YOU ROAM= If you are polite and show good manners, everybody will like you. (to ROAM is to go from place to place)

WISDOM= knowledge about how to best live life, deal with problems and relate with people.

WILLINGLY= If you do something willingly, you do it because you want to do it (no pressure).

RIGHT NOW= At this very moment.

ROLL YOUR EYES AT ME= If you roll your eyes, you look sideways and up in a quarter-of-a-circle motion and leave them high up for a second so most of your eye looks white (see picture). This movement means “oh my god, here you go again!”. If you are talking to someone and they roll their eyes AT you, they mean you said something stupid or silly or boring… again! Teenagers are the biggest eye-rollers in the world, sometimes they roll their eyes so often you think they’ll eventually come off their sockets (though that never happens, for good or for bad) and it can often look irritatingly patronizing. But if you have a child, get ready for lots and lots of eye-rolling.

WOULD APPRECIATE= Short for : “I’d appreciate it” = Please, that would be nice.

THE STUFF= The things (in this case, the food)

BURP= belch (to let air go out from your stomach in a noisy way)

I’LL SET YOU STRAIGHT= I will force you to be correct (probably by telling you off or by disciplining you)

UPON= on.

GET AN A= When you take an exam, an A is the top grade and an F is when your exam was not good enough. This is how it works in America and some other countries:
95-100 A
90-94 A-
87-89 B+
84-86 B
80-83 B-
77-79 C+
74-76 C
70-73 C-
67-69 D+
64-76 D
60-63 D-
00-59 F

GET THE DOOR= Open the door to the person who is knocking/ringing the bell.

DON’T GET SMART WITH ME= Smart (in AmE) means “clever”, so if you get smart at me, you try to be too clever with me.

GET A GRIP= Control yourself, don’t get too excited, too emotional, too angry, too silly, too anything!

GET A LIFE= Stop sitting there all day watching TV or playing video games or surfing the net, and go out, meet people, talk to them, do things with them, study, get a job, get married, live the real world which is waiting for you outside, and for god’s sake, don’t you ever again roll your eyes at me!!!

GET A PHD= Study at the university successfully.
A PhD originally means “Doctor in Philosophy”, abbreviated from the Latin “Philosophiae doctor”. In English-speaking countries, it is a postgraduate academic degree awarded by universities when you successfully finish your studies there.

YOU’RE GROUNDED!= If you ground a child/teenager, you tell them they can’t go out with their friends, etc and have to stay at home for one day or longer as a punishment (they can go to school though). For example, you child is 17, he goes out with his friends on a Saturday night but you said he must be back before 12… and he comes back at 2am: “that’s it, you’re grounded for two weeks. No, don’t say anything, not today, I’m really angry and now go to bed straight away… and I said STOP ROLLING YOUR EYES AT ME. Ok, you got it, now you’re grounded for a whole month and no, you can’t bring your friends home”.

FOR HEAVEN’S SAKE= For God’s sake = you use these expressions to emphasize the idea that you lost your patience or that you think it’s difficult for the other person to do or understand what you say.
-    I said “stop rolling your eyes at me”, for heaven’s sake!

IF ALL YOUR FRIENDS JUMPED OFF A CLIFF, WOULD YOU JUMP TOO?= You probably have a similar expression in your own language, it means that you shouldn’t do things just because your friends to it, you have to decide if it’s right or wrong instead of just doing what everybody else does (that’s one of the biggest problems for teenagers, but yes, I warn you, if you tell that to a teenager they will roll their eyes at you, of course).

IF I’VE SAID IT ONCE, I’VE SAID AT LEAST A THOUSAND TIMES BEFORE THAT= A common expression when you have repeated the same thing many many times but your child still pays no notice.

DNA= Deoxyribonucleic acid, the chemical structure which codes our genes inside the cell nucleus. So our personality (at least part of it, the predisposition) is coded in the DNA.

PJ’s= Pyjamas (a kind of soft sweater-and-trousers set used for sleeping).

HUG= A hug is an embrace, when they put their arms around you and hold you for a moment to show love.

BECAUSE I SAID SO= Because I am the one in authority and this is an order, I don’t need to give any reasons, just do what I say… and for God’s sake, if you ever roll your eyes at me again, even just one single time, I swear I will snatch that biddy-wally nilly-polly mobile of yours and I’ll break it into pieces with my bare teeth, and you will not be allowed to have another mobile phone till the day you are old enough to buy your own house or the Judgement Day, whatever comes first! GET IT!!!