What did you want to say?

I understand it. I don't find it particularly funny, but I know many people whose English is worse than a five year old. It is s good way of explaining your situation. I would say 'worse' rather than 'less'; speaking less can also mean that you are a quieter person, 'worse' only means one thing.

Yes, I think it makes sense. It means that you don't find funny something that was meant to be funny, for example, a silly joke. But it sounds informally, you may say this to your friend but should not use it in a formal situation. Please note that I'm not a native English-speaker, so it would be better to wait for a answer from a more competent person.