If you want to extend demo match time for PES 2020, you can use sider 5.4.2 - most of its features won't work with PES 2020 demo, but
match.minutes actually does. You just need to disable explicitly all other sider features in sider.ini, and specify correct exe.name. Like this:
debug = 0
close.on.exit = 0
start.minimized = 1
overlay.enabled = 0
free.side.select = 0
livecpk.enabled = 0
lua.enabled = 0
exe.name = "\PES2020.exe"
; enforce number of match minutes here
; you can set any value from 1 to 255, although you probably
; do not want to go higher than 90, because it will be weird :-)
; 0 - disables this feature.
match.minutes = 20
This example config gives you a 20-minute match.
Repackaged Sider 5.4.2 with already prepared config like the above: https://mapote.com/pes/sider-5.4.2-pes2020-demo.zip