As you have been situated in Germany, I guess your application was to DFG. Their rejection rate is rather high, as there are much more applications than funds available. You should consult with an experienced colleague which other possibilities are available in your field. There are more organisations funding science, and the same (or a similar) proposal may be succussful with another one.
Hi! Sometimes the success of proposals with solid ideas depend on how well this can complement the funders objectives, country context and so on. Certain research ideas might seem to be very demanding in developing countries compared to developed countries that attract funders easily and vice versa. There are always multiple factors associated to the successful project funding. Thanks!