Pay off the building loan first or continue saving for ETFs?

Hi everyone, I would like to hear your opinion on the following scenario, as I am not sure whether I have a proper overview of all the relevant aspects: There is a real estate loan with a total term of 29 years. The fixed interest rate is ten years and the interest rate is 3.51%. The loan is repaid monthly. There is also the option of making a special repayment once a year. In parallel to the normal repayment, a savings plan is regularly invested in a World-ET