Hi Marko,
I am trying to create post and I don't see Add Block in upper left corner
I checked your settings and it seems that you are currently using TinyMCE editor. Blocks are only available in the EasyBlog built-in composer. If you would like to use blocks, you would have to switch to EasyBlog built-in composer instead to create posts. The setting to switch composer is located at
Settings>General>Composer>Composer Settings>Composer Editor
I also do not have all categories to chose from listed on the right side, only main category.
I checked your composer and it seems that you are able to choose two categories currently. In the backend categories page, I found that there are 2 unpublished categories(refer screenshot). If you want to be able to select those 2 categories when making new posts in the composer, you would have to publish those categories first.
Hope this helped you understand more about your issues.