How is taxe fonciere calculated here in France?

Could you please tell me what the amount of taxe fonciere is based on in France. We have to pay 3,905 euros this year, but for what and how do they base that figure on my property. How do they come up with that figure? If it is on earnings well then, that would explain why we are broke and we have not paid the living tax yet. Basically, the work we have done this year has gone to these taxes.

If I declare it would I have to pay tax on it? It is coming to the end of the season now and work dries up for us. This has been the same for the last two years but when we ask at the Tresor Public, they are not very helpful. We are not earning hardly anything for ourselves and have to dip into our UK savings.

I have recently been diagnosed bipolar which is a serious illness. I have two Letters from my general practitioner and a consultant expert in this illness. I applied for Disability aid with RSI and was told they had rejected my application. How do and who do I appeal? Would you be able to advise me please? I live in France for over 5 years, I pay my taxes (all of them) and I can’t get any help from the system I pay into, that cannot be right, surely.