and do NOT say orv ( ̄へ ̄)
Main story completed side stories ongoing https://www.mangago.zone/read-manga/the_world_s_best_engineer/
The manhwa is good but i would suggest that u read the novel https://www.mangago.zone/read-manga/trash_of_the_count_s_family/
Technically he self sacrifice for his own gain but along the way its for the benefit of the others too https://www.mangago.zone/read-manga/eternally_regressing_knight/
Double regression manhwas? / two regressors?
'Debut or die'
'When the third wheel strikes back'(unsure about this, and also the manhwa is dropped so it only has novel, pretty good story tho)
'I will change the genre'(this ones a bit complicated with plot but similar)
'My in-laws are obsessed with me'
'Broken Ring:This marriage will fail anyways'-- this ones a bit of a complicated plot but is similar to your desc.
Shoujo, father-daughter manhwa (kinda), mc is half dragon & is super young, father is a top tier mage (?) and doesnt believe mc is his daughter and neglects and hates her, mc is friends w her fathers assistant
Rough storyline: dragon mom and mage father defeat the demon lord but dragon mom runs away w/o telling mage she’s pregnant, mage assumes she abandoned him and so he restricts his heart from feeling emotions, 5-ish years later daughter wants to live w father
Old school style, mc has curly (almost afro) hair, psychological manga
I don’t really remember the plot but I think it’s about the mc solving problems?? I don’t rlly remember..
Found it!! Had to scour Reddit for this one lolol
https://www.mangago.zone/read-manga/mystery_to_iunakare/
Read it a while ago but I rlly enjoyed it
Manhwas about/containing an older male and a younger child (in a familial sense)
Literally every other child Isekai manhwa but .. if u want something diff
https://www.mangago.zone/read-manga/single_dad_in_another_world/

Maybe just me but when I got logged out, I didn’t realize how bad it was to read on here without an account?? I couldn’t click anything without getting transported to another sketchy site
How did I live without an account for a year