How can link my Selve window blinds?

Maybe the first thing you should do is search the forum and the App Store if you haven’t already.
If you don’t find anything, search the internet to see if it is possible to control the Selve devices with a 3rd party gateway:


So it looks like it is generally possible to connect the Selve Home Server 2 with other gateways. However, if there is no special Selve app for Homey, you or someone else would have to program an app.
If you can’t program an app yourself, in this thread you can ask other users if someone would be willing to program an app. However, there is no guarantee that anyone will do that.
Now I have already invested a lot of time, which should have been your job.