Taxes for rent income abroad: double taxation?

I own an apartment in Germany and I’m considering buying an apartment abroad for investment (Italy or Spain).
I live and work in Germany.
How would the income from the rent be taxed?
Germany has ‘double taxation agreements’ with many countries (see [here](https://www.settle-in-berlin.com/income-tax-germany/how-to-do-avoid-double-taxation-germany/)).
After reading many articles online, I came to the understanding that it works like this:

1. Pay taxes on rent abroad
2. Declare the income again in the German tax declaration, but I can deduct the amount already paid abroad.

Is this correct?
Has anyone experienced this situation?
Is there a consulting company that you can recommend?

Thanks 🙂