Thanks a lot :)
I would like to pay off at least 3%!
Why? You have a little over 30 years until retirement. With 2.5% you will manage well. With some luck, you might get an even better interest rate than the 1.2% I mentioned, then the rate can be reduced even further.
From my point of view, the rate should be kept as low as possible (but as high as necessary). If you then want to pay off more, you do that via your special repayment right. The latter is usually offered by almost all banks for up to 5% p.a. free of charge. For 500k, that is at least 25k per year. You can therefore pay more than 2k extra each month than you have to.
I would always design the financing to be as flexible as possible. And that includes
planning and also using the special repayment right sensibly. If you then want to save compulsorily, you simply set up a standing order to the special repayment account. However, it is up to you whether you want to spend the extra 300€ this month on something else.