Is it right to think when you learn one language completely, then it is very easy to learn other languages?
Like today i am watching php tutorials and i see it's just syntax changes and everything is java despite of it is interpreted

Depend on the languages, partially. For instance, come to R or F# when you have been working in Delphi and Pascal involves a much bigger conceptual leap.

@halfflat ^^ pretty everything that i was expecting.
And bro is it good thought to learn every language out there so you can work on every single platform like android, ios, web, IoT and AI.
Or is it wasting of time and i better just stick to few languages and be just professional in them??

This is highly depend if the language are more like oop or functional imo

C based languages are all very similar.
So moving up and down and even sideways on the C tree isn’t to complicated once you know one or two of the languages and understand OOP.