Yes, "for" is correct. Before a noun or gerund ("-ing" word), you will always use "for" in a sentence that is like the one you gave.
"You can use the Internet for learning."
"They use the Internet for fun."
"She used the Internet for dating."
But before a verb in a similar sentence, you will use "to."
"You can use the Internet to learn."
"They use the Internet to contact old friends."
Your last sentence is grammatically correct (other than the typo in "possible"), but it is not idiomatic. I would write something like:
"You can use all available methods to learn English and always try to learn as much as you can."