Evaluation and Improvement of the Financing Option

You have the different variants and change the interest rate e.g. after 10 years, 15 years, 20 years (exactly when the building blocks expire from the fixed interest period). And then the total amount of interest paid changes over the entire term. As soon as the sums of the different variants become equal, you have the break even. And at some point you simply pay more interest with the other variant. There are also ready-made functions in Excel for this, but I never understood them or they do not work properly.