Raster calculation on 2 rasters with different size and resolution

I've got 2 raster files with different resolution and size. I want to make some calculations between the 2 rasters.I have already tried adjusting both grids to the same size and resolution (export of each to a new raster) and then performing an operation, but without succes.I am not a GIS expert and certainly not a programmer. Is there a simple solution for this?