morning,
how am I supposed to answer this now if I am not allowed to post company names and links here? Just google "Reparaturmörtel Silikatputz" and read the data sheets of the plasters you find to see if they are suitable.
But seriously: since the first amateur plastering has already failed (if I understand correctly), do you really want to continue on your own? Applying a thin decorative plaster is actually one of the easiest tasks; with some practice, you can manage a complete 8m wide, 7m high gable wall alone and without breaks in 6-7 hours flat out. Breaks are taboo because of the breaks in the plaster. You jump from one corner to the other to prevent all starting points from drying. If you don’t do it alone but with several people, the result is often suboptimal. I always find it hilarious when I go to construction sites where, because of so many multicultural workers on the scaffolding, you can’t see the facade at all. Everyone rubs around as often and as "nicely" as they want. One likes it diagonal, another sideways, the next overworked, the one after that just slapped on, and so on. Then you have the handwriting of a dozen unskilled helpers on one facade, who are advertised by the company as "experts."
Ok, I am also a 99% do-it-yourselfer, but I didn’t start with house walls when plastering, but with underground basement wall plaster, which was covered with bitumen, i.e. my quality mistakes on the surface were not serious. Gradually I improved and only after some practice plastered the first house (base coat 20mm + fine decorative plaster 3-5mm). By now, after almost 20 years of amateur building and at least 100 tons of various hand-applied plaster mortar, it’s routine. But you have to get there first.
If you want to hire a company anyway, have them do base leveling as well. They should also know what to use for that.
Regards
Allrounder