Agree with reducing white space in header a bit.
I would argue that the slider should be scrapped completely and not used. The way the articles are set up, it seems rather redundant, not to mention sliders are so overused. I mean it seems kind of odd looking at Saint Martin and having that same post right below it.
The tags should also be scrapped, when there is one post in a tag, it isn’t a useful navigation. They also make the sidebar too long on short posts adding a ton of white space.
The text in the sidebar is too light, I get that it is probably not trying to draw attention, but still it is too light.
Most important, scrap the /wordpress/ out of the URL. Ideally you would want this to be accessible from the root domain https://travelboulevard.be unless a different site is going there then /blog/ or /travels/ or something more useful than /wordpress/ as a directory. You can change this, but it takes a little finesse (instructions in codex), don’t just rename it.