I didn't know that you were serious about it.

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hi,
please find some mistakes in my sentences (especially I mean that, to)

I didn’t know that it is serious to you

I didn’t know that you were serious about it.

I didn’t know that it was that serious to you.

Thank you very much
The site is beautiful

George

2

I think your first sentence should read “I didn’t know that it was serious to you”.
The other two are o.k. to me.

3

Hi. Tort is correct.