Thanks for your reply, My answers in bold:
Does this happen:
- in other themes apart from Boost? YES , ALSO OTHERS
- on other systems with a 4k screen? I Haven't checked yet
- when you shrink the browser window less than a 4K resolution? I Haven't checked yet.. I've just asked the teacher to check it for me , when he will answer I will write back his answer here.
- in other web browsers? YES