When the co-author of a potential paper is not responsible I am a math postdoc and my young mentor is unfortunately a lazy person. I have prepared a manuscript 4 months ago and still no news about revision of that from the mentor. I do not know what can I do. Is it good to find someone else to help me to finish this paper? Sometimes the unknown referee suggest some ideas to improve the paper, Can I submit it to a journal and waiting for referee report?
The answer to your question is the same as for 50% of the other questions on this website: Talk to your adviser. Find out what the hold-up is, how you can help, what other roles you could take on in the lab to free him from work that holds up his side of the collaboration. Communicate about what your issues are.