Changing in onlineshop at link under the price Text. now it is "preis auf Anfrage" you need to change to a other text I will give you. now when I write in admin the price of 0.00 it shows "preis auf Anfrage" you need to program that when I enter 0.02 it shows a other text. you need to login to the database SQL . I am not shure about login. I can give you passwords and you need to try.
You must be very shure in MySQL. there will be no more infos about this job. Just do it without many question. no wasting of time. you have to do it till finish.