Hi, this is my first post in this forum.
I have problems when I have to do inversion:
I give you an example my grammar book has:
-When I saw his girlfriend I realised I had met her before
-No sooner had I seen his girlfriend, I realised I had met her before.
We can't do anything with these examples from your book - you need to give us some samples of your own writing, or ask specific questions about what you've been studying. If you do that, we will be here to help!
P.S. In American English, the second example would be: No sooner had I seen his girlfriend than I realized I had met her before.