tThe sScreens The Screens

Since it is a title, it should be capitalised.

For theym, it is very bad because they screens caused brain hurtdamage and eyes damage. For them, it is very bad because the screens caused brain damage and eye damage.

Since the pronoun representing the children (they) is the object, the pronoun should be changed to them, because them is the objective case, it is more suitable. The pronoun representing the screens is "they", but because this is a fresh sentence that has no mentions about screens yet, "they" should turn into "the screens". We are talking about abstract concepts here, so "hurt" should be "damage".

For theyIt is very bad for them because they caused their brain hurt and eyes to hurt. It is very bad for them because they cause their brain and eyes to hurt.

For theyIt is very bad for them because ithey caused brain hurts headaches and eyes pain. It is very bad for them because it causes headaches and eye pain.

Too the blue light makes them stay awake too. The blue light makes them stay awake too.

The "too" gets shifted to the end of the sentence. The blue light is one thing, so it should be "blue light makes' instead of "make".

Too themuch blue light make them stay awake. Too much blue light make them stay awake.

Too the blue light also makse them stay awake. The blue light also makse them stay awake.

They do not sleep more than 8 hours. They do not sleep more than 8 hours.

We are comparing here, so than is used. (Since it is showing a quantity not more than 8 hours)

They do not sleep more than the required 8 hours They do not sleep more than the required 8 hours

They do not sleep morefor more than 8 hours They do not sleep for more than 8 hours

Some experts says that the screens isare bad because the young see onth look at the screen morefor more than 8 hours. Some experts say that the screens are bad because the youth look at the screen for more than 8 hours.

Since "screens" is plural, the auxiliary verb "is" should agree with the tense of the subject; therefore, it is not, it is "are". The Youth is more used than The Young. Look is more suited in this context, and add some extra prepositions and quantifiers.

Some experts says that the screens-time is bad because the young see on thetare at a screen more 8 hours a day. Some experts says that the screen-time is bad because the young stare at a screen more 8 hours a day.

Some experts says that the screens time is bad because the young see onlook at the screen for more than 8 hours per day. Some experts says that screen time is bad because the young look at the screen for more than 8 hours per day.