Special job for VirtueMart?

[zoro17]

Dear forum,
maybe I have a special job for VirtueMart.
It's about a free car rental for specific temporary events.
To fit this job to VirtueMart I would use the product categories for these events.
A new event would be a new product category. When an event has ended the product category will be offline.

I need a special product category with all available cars.
An event will get cars out of this special product category.

A product would be the cars itself. The price would be 0 Euro, the stock is 1.
When a car is lent to somebody the stock would be 0.
Some hours later the car will come back. That means the goods receipt is 1 (no take back of goods).

I tested this scenario with Joomla/VirtueMart (latest versions) and I had no problems to define the
product categories (events) and products (cars).

And now my questions:
Will I get problems with these product costs (0 Euros) using the VirtueMart workflow later on?
Can't use the catalog function because I have "outcoming goods" when a car was lent.

The next thing is that this application will not use the VirtueMart shop frontend.
I need only the administration part of VirtueMart for planing the events (product categories)
and to administrate the car pool and the cars itself (products). This would be the part of a VirtueMart "Product Manager"
separated from a Joomla admin or a global VirtueMart admin. For this person is is not necessary to know that
he is working with a Joomla/VirtueMart installation. This "Product Manager" needs his own login.
Is it possible to do that?

The workflow of "lending cars" will be done by a web app or native app. The means that I have to know something
about the database structute (list of product categories, products). I have to do the outcoming and incoming goods
(lend a car and get it back). Where can I get informations about that?

At the moment I don't know whether I have to use an english or german frontend language.
Using german I can see some translation problems with VirtueMart. I dont't use the function
"Nicht übersetzte Programmtexte in Englisch anzeigen" but I have these english text blocks.
What can I do?

I have some (german) warnings:
"Keine Shop Währung definiert! Gehen Sie zu http://xyz1/administrator/index.php?option=com_virtuemart&view=user&task=editshop"
I think that have defined a currency but nothing happens. What is my problem?

COM_VIRTUEMART_MISSING_FLAG
I think this depends on the currency problem!? Am I right?

Do you have more hints for me to do this application with VirtueMart or should I use a different (shop) system?

Please give me a short feedback.
Thank you.

Kind regards

[zoro17]

Hello,
I solved the problems with currency and COM_VIRTUEMART_MISSING_FLAG.
Also I found the relevant tables in mySQL concerning the stock handling...

At the moment I need an advice to create a store manager user in Joomla for VirtueMart.
This person should be able to change poduct categories and product. Also the goods in stock.
He is not allowed to change anything in Joomla (frontend and backend).
Is it possible to do?

Thank you.