There isn’t a grammar forum on here, I'm afraid. Do you have any books on the subject?
English Grammar for Dummies was recommended to me by EmmaD and it’s very good. Also, while not a grammar book as such,
The Oxford Manual of Style is indispensable for settling things like the difference between ‘effect’ and ‘affect’, when to use ‘whom’, and so on.
There’s another one which is generally referred to as
Strunk & White, but it’s not to hand and I can’t remember the exact title. I'm sure someone will tell you, and you’ll get lots more suggestions when the rest of the UK wakes up
Dee