New member and lots of problems

Hi, I am a volunteer at a not for profit club and have purchased as a donation a new Casio QT6600 Pan Euro Version 1. By trade I am an Auto Mechanic and have no training in restaurant or cash register. I had lots off problems with the company in town that I purchased the system from and found out early on that the programer did not know the system. He set some things up but I have learned lots over almost a year that I had the system sitting in my house. Last month I set it up in our pub and am using it to some extend. I also have purchased the CV-33 programing. Now come my problems.
1. Every ones in a while upon loging in the system reprograms itself to the 2nd PLU price schedule, I have no prices in this level and had the wrong tax added at first. I changed the tax setup, so if it gets missed by the bartender, it still gets the propper tax. I have to reset every bartender several times a day to set back to the main PLU. Why is it resetting on its own? At some time I would like to use the 2nd PLU, but only ones everything is working propperly.
2. With "0" in my inventory the program gives me an error stating no inventory and we cant sell the item. I need to control the drinks with my inventory, but food items are not suposed to be in the inventory.
3. I put beer and other drinks in the inventory and insted of deducting my sales from the inventory, it adds every sale to it.
I have to program all inventory related changes on my terminal, as the CV-33 program dose not download it from my terminal, but uploads a "0" inventory.
Also I am not able to use my printer with the CV-33 program, I set my printer up, but it is not enabled.