Provided you have more than average skills with fine mechanics, it can be done.

The lens focusing mechanism has a couple of guide rails, which are probably loose and must be reattached in order to have it working normally again. When the second of them came loose, focusing became hard, as the focusing rail probably would twist and not be aligned when turning the focusing ring.

To get things back into the envelope, you first need to disassemble it further. Then you can again attach the guide rails.

The stop for focusing movement must be removed to put the lens back in, when the guide bars are in place. Then the focusing helicoid is turned a bit past the close focusing mark, and the lens pushed in from front. Turning back the focusing helicoid will set the lens in its position. You might need more than one try, as you might put it into the wrong helicoids - it has several "threads".

When putting it in, you must make sure that the stop-down mechanism for the diaphragm also engages.

When you have got it into its correct position, the screw for stopping focus movement in the close end shall be put in place again, and the lens will then work normally if you haven't damaged anything or lost parts.