As I gain more experience working at this team, I have been eventually onboarded to work on different projects with different contexts, and finally arrived at a point where multiple bottlenecks kick in at one time. For example, I need someone(s) to unblock me, do knowledge transfers, while they are typically very busy; I need to spend time on building understanding on new stuff on my own; I also need to spend time on undocumented work (being a resource to other engineers for some of the work I have done, unexpected work request (enhancements, API revision...) flows into my plate, technical debt, review PRs, checking in teammates' progresses, planning and retrospect work efficiency improvement, and etc.). The goal is to make sure I am not blocking other's work, and deliver with speed and quality, as well as meeting Team's priorities (not even mentioning books and tutorials learning besides day-to-day tasks)
My manager has recently expressed concern on my delivery speed and quality, so what could be my next steps? Thanks in advance.