Seeing non SI units in this context makes me sick.

Can you pay in cash on “some house buying mobile app”?

Fartleks are usually prescribed without strict timings, rather you need to run them by feeling. To properly choose the right pace you necessarily need some experience. Do a fast pace to the next tree or just raise your pace a little and run to the bench you know is around the next bend in the trail. Mix it up. Have fun, enjoy running, enjoy the speed. You should never be too out of breath to continue running at low effort. If you feel like you started too strong, slow down. If you feel like you left too much in the tank, do the next one faster. You will get to know body better with time, if you stay consistent and healthy.

Buy the cheapest old computer on your equivalent of Craigslist and install TrueNAS. If you want to use a lot of drives, make sure there are enough SATA connenctions on the motherboard.