[sAmI]

And do you face any health issues such as dehydration, malnutrition, headaches and similar problems? Or does it usually go smoothly?

Since I know that you guys are probably used to it by now and won’t face many issues compared to let’s say if I tried it!

I’m also curious as to how long you need to fast for. Is it like a certain amount of hours?

It really depends on person wise, On what he is doing, for me i usually play football before 2 hours. But i actually never experienced a headache or dehydration issue. We actually eat meal at sehri or which is called Suhoor which is mostly around at 4AM in my city, After 4:35AM we cannot eat till up to 7:05PM and a minute to minute increases each fast.  I have seen many people working like in construction fields and in the sun and the ongoing heatwave hats of to them tho! There are actually no health issues as after 7PM we can eat or drink water much as we want to. 
And a life hack Most of the people eat yogurt including me so we dont feel thirsty throughout the day!

Let's say if you tried it i can say you would feel something on the first day like you would feel thirsty if you drink pretty alots of water through out the day!