I have no idea how to fix the format.
My Excel program began to behave strangely after the system virus was penetrated into the software of my PC, which is now found and neutralized by the antivirus. After some time, Excel when editing files began to often give errors about the wrong format and data corruption, which led to distortion of information in some files. For example, instead of calculations, meaningless symbols began to appear and the format changed. The Excel update partially solved the problem with the errors that were generated in the newly created files. But there were incorrect files that I have no idea how to fix the format. How to be?