if we are using future "will" in a sentence we can't use -ing after a verb I will do my homework now...

no, you would not say that. "i will writing my homework now" is incorrect because you are using two different tenses in the same sentence. "i will" is talking about the future, it is saying "I am going to do it" and "writing" is talking about the present - "I am doing it" so "i will writing" is saying in the future in the present so doesn't make sense As you have put "now" at the end of the sentence, i will presume you want to speak in the present tense, so you should say: "I am doing my homework now" You could say "i am writing my homework now'" but we don't say this in English as homework is something you do, not something you write. You can write for your homework, but you can't write your homework, for example " i am writing an essay for my homework" If you want to talk about the future you could say "I will do my homework" or "I will write my essay for my homework" -This follows for most things- I will do (future) I am doing (present) i will write i am writing I will eat I am eating I will swim after lunch I am swimming I will go to the park i am going to the park And hopeful this won't confuse you but you can then say I will go swimming after lunch i am going swimming

I'm going to do my homework now or I'm gonna do my homework now