I can tell you

1 我可以肯定地说

I'm telling you I tell you

2 确实

all right real true certain absolute concrete distinct cast-iron unquestionable undoubted just really sure actually simply definitely truly honestly precisely decidedly forsooth certainty beyond any doubt I'm telling you ever ever such a ever so such a goodness knows I tell you straight up beyond doubt God knows near enough if ever there was Heaven knows if ever there was one

3 我敢说

I'm telling you I tell you