I learn on the phone with a chavrusa while driving home. He reads and I listen. Sometimes after a long day of work my mind is exhausted and I have trouble concentrating, but he keeps reading. I don’t ask to him to repeat since it won’t go anywhere. If I postpone though, we’ll never get through the mesechta.
We just finished a mesechta. Originally we were going to do a siyum together, him saying hadran and me saying kaddish. Now though, we’re doing a separate siyum. Is it a problem for me to make a siyum myself being that I phased out on some parts?
One of the reasons we make a siyum is in order to give chizuk to the person that worked, and to encourage him to continue. This definitely applies to your situation. Learning on the way home from work, is not easy, and although there were parts here and there that you didn’t concentrate, nevertheless you can still make the siyum. Regarding the kaddish however, should say the regular kaddish d’rabonon, that is said after learning, and not the kaddish of bolma dischadita.
Mazal tov and best wishes