Is a school still necessary to learn a new language?
Do you think that nowadays a language school is necessary to learn a new language? Or do you think you can learn it with all the information out there on the internet and learn by yourself? If so, what are some tips to do it?

not really I think practice is the best way to learn a new language

There are apps like Duolingo that can help you learn a language.

Nah, apps and podcasts are a good way to learn though learning in person can help with practice in the beginning. Also if you don't practice or use the language enough you'll start to forget words, or phrases, so if you do plan on learning a language, choose one that you are very interested in and can continue to practice.
Looking for online friends that you can do language exchange for practice is one good way for you to get better and they can point out your mistakes.

if you want to have a certification showing that you did indeed learn the language then generally you will need to go to a school/take classes for it. but if you just want to be able to speak/write/read then no, definitely not. Duolingo, rosetta stone, babble, etc can all help you learn various languages. none could probably make you 100% fluent though, but neither would most classes