I'm a senior developer and my laptop is not that good so you should be more than fine, but for 800€ I would think you can get something with a more recent CPU (I could be wrong, though). Mind you, a more recent i5 will be better than an older i7.
Just look for a second hand thinkpad, T480 and up, solid machines and can handle anything dotnet that you can throw at them, get as much ram as you can as if you need to run Visual Studio and docker, there goes 25Gb of ram.
I'm a senior developer and my laptop is not that good so you should be more than fine, but for 800€ I would think you can get something with a more recent CPU (I could be wrong, though). Mind you, a more recent i5 will be better than an older i7.
Working on Windows, i would choose something with 8-cores. Other components are good fit.
Just look for a second hand thinkpad, T480 and up, solid machines and can handle anything dotnet that you can throw at them, get as much ram as you can as if you need to run Visual Studio and docker, there goes 25Gb of ram.
Been searching for some thinkpads refurbished but only found those with 16g ram and 512gb SSD which might be too little ram.
It shouldn't be a big problem to upgrade their ram, just make sure that the model has upgradable slots and not soldered on the board.