Brown spots on my fava beans
That looks like chocolate brown spot to me. It could also be broad bean rust, but then there would be a yellow halo around each spot.
Either way it is a fungal disease. If it is not very severe yet, remove diseased foliage and throw it in the trash, not in your compost pile.
Try to keep the plants as dry as possible, i.e. when you water, water the soil only, not the entire plant. Drip irrigation may be the way to go here.
If your plants have not produced any beans yet, you may want to consider spraying with a fungicide that is labeled for vegetables. Since you are outside of the US, I do no know what to recommend. If your plants are done producing, you may just want to consider getting rid of them right now.
At the end of the season, make sure to clean up your plants really well. You may also want to rotate your crops.