I think this is the first one
https://www.mangago.zone/read-manga/the_good_teacher/
The first one that you described could be "The good teacher" ....and the second one is actually from a collection BLs with older uke and the story you described is the first chapter , it's called Ureoji BL
this is it!!! thank you sm ╥﹏╥
Thank you for the extra infos! btw do you have more older uke in ur list that u can recommend?
Here's all I can remember, but try Searching the other works of the author of Ureoji BL , the draw the best older uke
BL with older ukes-
Never good enough
Long time red mall
Baby face monster
Papa is a bride
My purfect boss
Katsubou animajemera
Oni to tengoku
On doorstep
Houtou musuko to koi no ana
Lucky paradise
Melt at night
Love & hate
Boku no omawarisan
but there is this one BL manhwa its BNW(non colored if I remember) where the uke is a teacher and he teaches this retriever pup like seme into the adult world. Also a BL manga where the uke is older and bestfriend of the father of the seme then they got caught doing it in the couch