I'll fix this

[Marina Gaidar]

Can I say "I'll fix this" if I promise somebody that I will improve some bad situation which arose because of me?

[Gillnetter]

Can I say "I'll fix this" if I promise somebody that I will improve some bad situation which arose because of me?

Yes, that is fine. You could also say "I'll fix this" for a number of different reasons. If, for example, an automobile won't start, you could say, "I'll fix this".