Sometimes I get feedback from marketing communication consultants that the English in my presentations needs to be improved in order for it to become proper "marketing English".

I consider this a compliment. "Marketing English" filled padded with buzzwords and long, elaborate sentences is making every product brochure or presentation in high tech sound pretty much the same.

I do recognize though that I am not a native English speaker, and that a native English speaker can figure that out after reading just one sentence on a slide. But I am not communicating in "proper English", but rather "global business English", which I picked up at business school back in France. It is a subset of English with a vastly reduced vocabulary, just enough to communicate important business concepts to other non-native English speakers. (I am not there yet with business Hebrew though).

If you are not a native English speaker, don't try to force a "grander" language on yourself, instead, it is OK to keep things simple and direct. Fix those typos though (I admit that I can be sloppy here as well) and yes, it never hurts to ask a native English speaker to glance over your text of an important presentation. Then decide what advice to incorporate, and which suggestions to ignore.