I'm not convinced.

> In the past, the severed heads of these Berber bandits covered the ground of the palace at Sijilmasa; there were highwaymen, then, who stopped you across the Sahara en route to the Land of the Blacks.

I don't know what's trying to be said here.

Is english your native language? This seems like a pretty straightforward sentence.

What's confusing you?

It is a confusing sentence. Semicolons are stupid and shouldn't be used anymore. It has a random "then" thrown in there for no reason.

Try reading it out loud. Keep in mind that the original is in French and this is a translation of that French text so you are probably more at war with the translator than with the writer. Even so, to me - also a non-native English speaker - there wasn't a sentence in the article that I could not understand, sometimes it just takes a bit more effort.

A bit poetic maybe, but it sounds fine to me. Maybe because English is not my first language.

I am not a native speaker and always eager to improve. I understood the "then" as "at that time (in the past)". Is that wrong?

That is correct.

I find the sentence very confusing, but I don't think it has anything to do with semicolons. It just seems like unclear writing to me.