I built my own website a few years back and have been growing and tweaking it for a while. Initial desgin was probably very flawed. Performance tests and google mobile friendly scores are not great on my website. To try and improve it recently I have:
Cut active plugins to 14
Updated php and workpress to latest
Tested several wordpress themes (I settled on Ocean based on my limited skills and familiarity with Elementor as the main builder)
Installed Hummingbird pro and followed the advice I understand (and experiment with lots of settings but to little positive gain based on my lack of deep understanding)
Installed Smush Pro and followed the advice I understand.
Removed or cropped all my images or converted to jpg (or next gen if I understand Smush)
I know that upgrading the server would help and I do aim to do that as finances allow. Any other advice?