When To Move On From A Project?

What metrics or factors are most important when deciding if a project is worth continuing or not? I am 24 and have been working on a project for about two years now after work and on weekends. Although two years is a long time to work on a project, I found it justified. On first launch, we organically obtained 300 users in two weeks, 40-50% of users were consistently active and paying customers, doing well on socials etc. Customers were giving voluntary, overall very positive feedback about the platform. Nothing crazy but enough to validate the idea. We ended up having to bring down v1 and pivot semi drastically and have been working on v2 ever since. At the time, I was working on the platform with a lifelong friend. He did the frontend/design while I did the backend framework, database, cloud services, servers, data visualization, etc. I also do all the social media, content creation, promotion, legal, administration, etc. However, he has now decided not to work on the project anymore, leaving all the remaining frontend work to me. I know nothing about frontend, so I am at a crossroad. On one hand, I could find a frontend cofounder. As I'm sure some of you know, easier said than done. I see this process taking at least a couple months, most likely more. On the other hand, I can just take 6 months and learn frontend technologies so I can finish the project myself. I don't see anything from a "startup metrics" standpoint that makes me think I need to move on to something new from that perspective, but I am starting to wonder if it would be more worthwhile to build something I am more capable of finishing front to back myself, and in less time than it would take to learn frontend and continue the project. How do you decide when it is time to move on from a project? Where is the balance between learning what you need to get it done and wasting time learning something you should bring in help for? Any advice is much appreciated. \*\*EDIT: Way too long