Can i learn and master both web and app development??

Answer 1

Sure, why not?
If you will practise both and keep your interest in it, there won't be any problem ^-^

Answer 2

In my opinion the word 'master' is heavily overused in contextes like this one.

Being a master means being the best of the best of the best! Of all the people trying hard to get there!

'Can I become a master of the violin and the piano?'

Very likely not, because if someone practices only one skill the same amount of time (like 20 years full time), they will have put double the work into one skill.

But can you become well enough to be productive?

I'd say yes, as long as you invest enough work.