Updating social security contributions

In September, I switched from my main occupation to a secondary occupation as a self-employed person. My social security contributions were then updated. Now it is a new year and I am receiving another proposal for social security contributions based on my income as a person in my main occupation. Obviously, this is no longer correct and I want to pay less quarterly. Now I have to apply for a reduction myself, but I have to base it on estimated income for 2026. Personally, I find that very difficult. How do you do this? (Before, my accountant told me how much social security contributions I should pay, but now I have switched to dexxter). Thank you in advance!