"As a non-native speaker myself", just learn how to type in that language. If anything, capitalize what needs to be capitalize. Learning how to punctuate and further differences between words/general grammar comes with time and, of course, with who you talk to.
if u talk wth ppl whu tyep l1k3 th1s ull prolly type like th1s
But if you talk with people who talk like this, chances are you'll adapt to it. ;3