Should I focus on a specific programming language or should I know the basics of the most used ? and what programming language do you suggest ?

Typically all programming languages are the same, just a slight difference in the syntax,

you should know the basics of the most used programming languages,

for beginners i'd suggest HTML, Javascript, and once you've learned these you can go to PHP but a little more difficult to set up but PHP opens up new doors for you since it is based on the C language and almost60% of the languages known today are based off of C,

hope this answers your questions.