I wanted to play with my girlfriend together a multiplayer game where you can best build a life and just has a joint project or something like that (please no Minecraft). It should not cost that much as I do not want to spend so much money on it and you should keep in mind that it only owns a laptop.
Try "Raft".
Dner / Felix from the store (https://www.youtube.com/channel/UCbuKwxnPVgjkWhYGtTeFPaw/featured) also plays this on his gaming channel with his girlfriend Kati ^^
No idea12,
That you do not want to spend a lot on your girlfriend, I just let it stand in the room. So I take games up to 60 euro in your search.
Minecraft:
Endless play, has a bigger project potential and there you also build up your "own life". With Modpacks, for example, Life in the Woods, the flow of the game is even more interesting.
Survival Games:
Most of them like Conan Exiles, ARK: Survival Evolved, Citadel: Forged With Fire, Rust, Empyrion - Galactic Survival, The Forest, Raft and so on are all endless games, but they get boring as soon as you get into the endgame has arrived. Because you practically play through them despite the endless play.
Sandbox MMO:
Like ArcheAge or Albion Online might be something for you. Here you could consider building your own villages. However, this requires a lot of work and, among other things, real money to accelerate the whole thing.
For the final decision I would only on Minecraft. But you do not want to get suggested. Nevertheless, I hope that my answer helps you.
I would not necessarily recommend survival games. There are only the hard people around who let noobs no chance. If Survival Game, then only PvE Server or Private Session. I think the best thing for you two would be either Force of Nature or Stardew Valley, which I would recommend the latter. It is the ideal game for couples and does not need many system requirements. Best to buy in a key shop. There games are much cheaper than on Steam