Not everything is on the Internet. Even most information from as recent as the 1980s isn’t. A not insignificant percentage has been digitized (this is an ongoing effort), but this doesn’t mean you can just google it or access it through a website.

If you know where and when your ancestors lived, hit up local, regional and national archives. Church and municipal records, national surveys, newspapers (useful for announcements of births and deaths alone), school and university records, etc. You’d be surprised by how much you can find this way. If you’re living too far away to visit in person, give them a call. Archivists are very helpful people by nature and occupation.

It’s fucked up, but you could try the Mormons. They do this thing, retroactive conversion, so someone becomes Mormon, and they go back and make all that person’s ancestors “Mormon”. So they have incredibly good ancestry records. Just a thought.

there are offices that offer these services offline. if you wanna do it on your own youll need to request a lot of acces to city archives. At least in some countrys, citys keep many infos. including if someone moves there ect.

So if you know where your grandparents used to be born, go there, and maybe you find infos about your grand grandparents. and then its just a game to hunt for infos. See if you can find your anchestors names in unis, or companys or something.

I heard its quite tedious and takes years

I like the collaborative nature of https://www.wikitree.com/

It depends on where they were from. If the big repositories don’t have the data (and you have clearly tried them) then:

• The data may have been destroyed or never written down. I am ¾ Irish but landing any of my ancestors in Ireland has been hard. The records burned in 1916 and, in some areas, there are gaps during the Potato Famine when no-one was around to write things down. One of my best DNA matches on my Mum’s side falls foul of the latter as we have matching surnames and know pretty much when and where our connection would be but the parish records just stopped in that period.
• It’s not in English. They are doing their best to fill such gaps but adding translation in can be hard. There are often regional family record offices but they may be in a language you don’t speak (I’m having trouble tracing my sister-in-law’s grandmother who was born in Estonia. I am also helping a friend whose grandfather was born in Malaysia and it is tricky even working out where to look). Scandinavian genealogy tends to be excellent, but you may need access to the “farm books” where the records are kept.
• It’s paywalled elsewhere - Scottish records need you to subscribe to a specific site.
• The names are badly transcribed - the British record keepers clearly struggled with some Irish names especially when being told them by illiterate peasants (possibly not helped by some being in Gaelic). I have one family whose name is written over a dozen different ways and it can be hard piecing it together. The names settle down after a bit (there was a big push for literacy in the late 19th Century) but there are two branches of the family that ended up with two different spellings of their surname.

Or any other issues. Without details it is tricky to point you in any specific direction.

If you hit a wall, try DNA.

Here only those data are available for search that are older than 100 years in case of birth certificates and maybe 50 for deaths. So you would need to know at least your grandparents’ birth data to start…