Hey,
The UMAT is an extremely tough exam and it’s perfectly ok to feel disheartened at times. I think when you are feeling this way, it’s good to focus on the positives. 79th percentile in section 2 is a great score, and bodes very well for your UMAT performance in the future as section 2 is undoubtedly the section most reliant on intrinsic ability and the medentry cohort is a lot more competitive than the actual UMAT cohort.
Since you rushed the exam and did it before reading any guides, your overall score is definitely not representative of your actual ability in the UMAT and you should not worry at all about your percentile. I think the fact you did an exam straight off the bat will work in your favour, as while many people will be beginning revision in an aimless fashion, you can get straight into targeting your weaknesses and making sure that you are in the best possible form for the actual exam. Five months is plenty of time to formulate and execute an efficient effective study regime for the UMAT, so really don’t stress about the time. I guarantee you that you are ahead of most people in terms of revision.
Good luck! (Hope the bio SAC goes well)