A friend who bred dogs once said that she often recommended corgis for “starter dogs” as being relatively easygoing. I’ve no personal experience with them, so I can’t vouch for that.
If you’re looking at purebred dogs in general: soft-coated Wheaten terriers might be worth a look. They’re going to be roughly the size you describe your dog to be, and they’ve supposedly got a really good personality. Some people compare them to Golden Retrievers, personality-wise, but with a bit of the terrier attitude. The only one I knew personally was very friendly. If I were to to be pet-shopping, that’s one breed that would make my short list, though I don’t know how common they are in Europe.
Of course if you’re looking for something with a similar body type to that of your current dog, a Wheaten is quite different.