I agree with kiev88user. You cannot focus that lens through an SLR.
We can see the lens will project an image from the posted scans. The best method is what kiev suggests, ground glass at the film plane & observe focus.
The Summar and Elmar do not have a focusing helical. it's a continuous thread.
It may be that the focus is off by being screwed in too far or not far enough. The infinity stop is a simple post screwed in place. Remove it and you can check on the GG as the lens is moved beyond it's normal limits.
If it unscrews, no problem, just screw it back in again. If it won't get a sharp image within it's range it's time to consider mis-assembly.