Top cover cleaning how and with what

[jona]

My top cover is dirty from tree leaves and what not.
I tried with regular water and and small broom and allthough it's much better it's not really clean.

I dare not to use any cleaning agents as im afraid to damage the
impregnate layer.
So my q'n is what can i do and use in order to get it as clean as possible without damaging the impregnate layer that has to be put on in a year or so (3 years) if im correct.
The outer fabric is unbrella 340 gr/m2 and TEX’AKTIV is being advised by the builder for reimpregnating the outer cover.


Any advise is more than appreciated.