Biology was one of the subjects I took during my A-Levels, and I won't lie but it was one of the harder subjects I took. During the first year (AS Level), I was genuinely doubting myself, wondering if I made the wrong choice. But I stuck with biology because it was a subject I needed for the university courses I wanted to apply to. I expressed my concerns with my biology teacher at the time, and thankfully she was really supportive. She frequently provided me with the extra prep and resources whenever I felt like I needed it.
But as I worked through all the prep she gave me, I realised how biology is a "memorising" type of subject. A helpful tip I can give you that helped me strengthen my understanding, was to go over your notes from that day when you reach home. I used this technique across all of my subjects, but I found it particularly helpful with biology. By revising the notes, and making additional notes from the topics I learnt that day; it helped me retain all the information for the long run. I made this a consistent routine all throughout the first year, which undoubtedly benefitted me a lot during my mock exams.
When second year came around (A2), a lot of the topics were building on the knowledge we had from first year. If you reached the point in AS where your understanding of the foundations are solid, then the transition to A2 should be a bit more smooth sailing.
Biology is difficult, but if you have the passion and if you're willing to put in the extra work- then you'll do just fine