vocal problem or?

After doing my vocal warm up, i can sing 4 to 5 songs finely,my vocal seems healthy and fine but after  a while my vocal dries so much fast and i can't even sing properly after that,can you tell me what is happening and what are some solutions for it?

Hi, Pemba! I encourage you to hydrate more than you normally would. Singing requires your vocal folds to function optimally, and hydrated folds are healthiest!

Thank you Camille;)but i also sometimes get that tightness in the neck after warming up my voice what i can do for that?

Stretch out before singing, notice when and where you're feeling tension or strain, incorporate some movement while you're singing (ie: gently and slowly shaking your head "no" when you start to feel your neck muscles tensing), and stretch out again once you're done singing. 

A good approach to reducing tension is to:

First pinpoint what is tensing! Then, either

(1) move those muscles to prevent them from tensing in the first place (i.e.: softening and mobilizing your jaw so it cannot clench, or slowly shaking your head “no” to prevent the neck muscles from “grabbing”) 

OR 

(2) remove those muscles from the equation (ie: preventing tongue tension by singing with the tongue totally relaxed, out of your mouth and resting on your bottom lip). 

The ultimate goal with all of the above is to let the correct muscles do their job without the "help" of those extrinsic muscles that are tensing.

Here's a full hour-long lesson I gave on strain and vocal health - check it out! https://www.youtube.com/watch?v=s6HRdzfpT20.

Thanks Camile for your kind response:)

My pleasure, Pemba!