Thanks for replies. It is defo slower then friend X5 next to it. It start after a few spins but them few spins should be in a few secs. I can count the revs of starter.

I will try the second hand starter. Apparently, same fault is on 7 series with same part number 7788680. 400A defo taken when spec claims around 180. So it could be only the starter. I can see previous owner put a large 110Ah battery to address the issue.