I am sorry to be the bearer of bad tidings but you cannot speak, write or fully understand English without a good grasp of grammar.
I always tell my students that if you think of vocabulary as the bricks of a language, grammar is the mortar that holds it all together and helps you build structures that won't fall down around your ears.
Some grammatical mistakes are not a problem but others can be disastrous.
Consider the difference between:-
"I forgot feeding the dog."
"I forgot to feed the dog."
One of these sentences is disastrous for the dog. But which one?