I found it a lot easier when I aimed a decent light at the weld area, even though the workshop is well lit, because you are in a corner and your hand/torch etc makes a good light stopper it's a lot darker than on the flat.
Inside corners in the workshop or up that corner you made in that wheel arch?
former look up the numerous T joint tutorials
for the latter, youll find that car panels never get welded in a corner the original panel nearly always has a return on it( flange) which is welded on to the other panel- copy that.
and work lights- head torch on your helmet, so there is light where you look, etc all helps led worklight at lidl soon, plenty of led inspection lamps on fleabay