I havent done a test like this before, and i must say that my results are higher than i expected.
This was my plan during the run; I started the first 10 min at a pace around 4:55min/km because that is around what i run at for a 10k. After 10 min i pushed harder to find a pace i felt i could hold out for the next 20 min. Trying to simulate a negative split.
What do you guys think about my run? Do you see anything i did wrong, or does this look right? Should i push a bit harder the first 10 min?
Yes, I think you could push harder next time for the first 10 minutes. This was a negative split, which always leads to the best results. However, your negative split was about 30 seconds (per mile) and the goal is 2% or less, or about 9 seconds per mile faster the second half than the first.
Consider dropping your threshold pace by 5 seconds per K based on this result, as I think you would have been there if you started out a bit faster.
No change to LTHR. Yes, even though you started slow, that first 10 minutes is really just o get the HR elevated close to LTHR, and the last 20 should be accurate for you.