Amazon PPC advertising campaign in Germany -- 2

We are a small company selling items on Amazon in Germany. We sell stress balls in packets of varying numbers and have 12 listings in Germany.
We advertise spending around 1200 Euros per month in each country on PPC campaigns through Amazon.
Our ACOS is very poor 36.44% and ROAS 2.74 and seem to be paying a great deal of money without getting any extra sales.
We need help -
revising and updating our current campaigns or
starting a new set of campaigns to improve our return
ongoing monthly work tweaking and amending the campaigns.

We require a person who is able to do the above
with a proven track record
be based in Germany
Because of time differences we will not consider freelancers outside the UK or the EU
Preferably the freelancer should be able to speak German