(Decided not to spam the comments section, so)
Using spoken english ( sometimes called 'being colloquial') is good - it makes your story more realistic. In real life, people 'hmmm' and 'uhh' and pause for confirmation from their audience and have bad grammar.
"I goed to the park," said Suzy
That's okay* if you've established Suzy as someone who isn't good at english, although, as Amadeus rightly pointed out, some people might find it offensive and be hurt by it.
When using phrases like "Am I right?" "You know?" etc, it's implied that there is both a speaker and an audience. This is why you can't use these in third person narration - who's the speaker?
In your first person past tense narration, though, you can do things like
"It's totally chill, I've got it," said Anu.
Although I didn't trust her to take care of it properly, I had no choice. I couldn't break my head on it forever, could I?
Both of those are informal phrases (although apparently 'break my head is very Indian - I figured you might appreciate it ;) ), and they're used in two different contexts - dialogue and narration (from a 1st person POV)
However, if you had something like
"Oh Em Gee! I just love this place! It has, like, the best, like, salad in, like, the world!!!"
That comes across as a stereotype and annoying - people who don't use slang will think it's unrealistic because no one says "like", people who do use slang will think it's unrealistic because no one says "like" that often.
*There's no real 'can' and 'can't' in writing. You can do whatever the heck you want. You can write in Klingon, no one's going to stop you. But adhering to conventions gives you a better chance of having someone read what you write.