Category Problem

Okay I’ve searched everywhere and am officially losing it. When I first noticed the problem I thought it would be an easy fix, but as always I had it wrong!

My website is a blog with four main categories names, ‘Blog’, ‘Downloads’, ‘Tutorials’ and ‘Quick Tips’.
Besides ‘Quick Tips’ all of these categories have multiple subcategories.

I added the four main categories in my main menu and on every main category page I have a navigation in the sidebar that allows you to navigate to a certain subcategory within that main category.

Example:
When you click on the Blog. You go to the page with all the blogposts. And clicking on ‘WordPress’ on the side navigation would send you to all posts within that subcategory.

But that’s where it goes wrong. It gets a 404 error. All the subcategory pages do.

So the blogpage https://chake.nl/blog/ works.
The article page https://chake.nl/blog/wordpress/test-5/ works.
Yet https://chake.nl/blog/wordpress/ doesn’t work.

I then found out that when I remove the ‘blog’ part I do get the right page. But I can’t imagine why the category in botht he post as the sidebar menu sends me to https://chake.nl/blog/wordpress/ if the correct category url actually is https://chake.nl/wordpress/.

Now I hope you understand my confusion. And I’ve tried disabling all the plugins and switching to a different theme and none of it fixed the problem.

My permalink settings are:

Custom Structure: “https://chake.nl/%category%/%postname%/”
Categorybase: “.”

((If I remove the dot then my articles are in https://chake.nl/category/blog/wordpress/ which I don’t want as well))

The best solution for me would be that the /blog/ is added inbetween so that the links are all correct. So now it is https://chake.nl/wordpress/ but I want it to be https://chake.nl/blog/wordpress/.

Sorry for this very long post, I just want everything to be clear. Hopefully someone knows the solution, as my website is about to be officially launched.

Thanks so much!