If people eat too much, they get fat. -correct
If I spoke English fluently, I wouldn’t
watch English TV show everyday. -correct
If I don’t pay my bills, I will have to pay an
extra charge. -correct conditional, but don’t forget the indefinite article
If you sit in the sun for too long, your skin get hurt. - correct conditional, but it should be “your skin gets damaged” (we commonly use ‘damaged’ with skin, not hurt)