I want to wear sandals but I have fallen arches any suggestions?

Yes. There are a variety of sandal manufacturers that produce sandals with arch support. Most of the good running stores will carry some. Some examples are: keen, birkenstock, fit flops, naots, think, mephisto, finn comfort and chaco. There are many others that can provide you some extra support. See what works best for you. Dr l.
Walk-fit. Walk-fit has removable arch support can insert into sandal -available for $20.