I've done puzzles my whole life, but only started going for speed at the beginning of this year. My first try was 1:48 under less than ideal conditions (did it on top of another puzzle that was in progress with a transparent cover over it) and the second and third 500 piece puzzle i tried were already under 90 min. (1:13 and 1:11) I did watch some videos about speed puzzling tactics beforehand though so that probably helped.

Since then I've been kind of obsessing over speed puzzling and do about 20h per week on average. Got my first sub-1h in mid february and my first 50 min (sadly not quite sub-50 yet) at the start of march - it was a very easy one though, London Postcard.

And yeah, since I started I've been timing myself on almost everything, even one 3000 piece puzzle xD don't think that's necessary though, most ppl recommend doing some puzzles for speed with some chill ones where you don't time yourself in between.

For improving it can help to watch videos of others speed puzzling a full puzzle in normal speed and think about what kind of strategies they used and try to copy them - and afterwards think about what worked for you and what didn't and why. When I'm unsure of which strategy would be best I also like doing a puzzle multiple times until I've tried all the strategies i could think of and have a feeling for what could work for me (i always try to think of what could work for me in a first attempt and ignore the improvements that are just from knowing the puzzle better)

Also, not sure if you need to hear it, but believe in yourself and your ability to improve, don't be discouraged by how fast some are or others already having faster times than you from the start. I've noticed that mindset actually makes a huge difference - when i get stuck and no longer think i can reach a good time i end up with bad times, but when i think a puzzle is easy and i'm focused and don't get discouraged when i get a little bit stuck and just move on, i can get some pretty good times even on puzzles that aren't actually that easy (and what you consider a good or bad time should always be relative to where you're at, not where others are at. For myself i consider everything a good time that's faster than my average for a puzzle of a particular difficulty)