It means "we are a little worried about what might happen, but we are hoping for good luck." It expresses optimism. It is friendly and informal; it is not serious or solemn. "I'm going to take my driver's test for the second time. I think I'm prepared!" "We'll keep our fingers crossed for you!" "It's clouding up. But I'm going for a walk anyway. Would you like to come along?" "Sure." "It might rain." "Well, we'll just keep our fingers crossed that it won't." People literally cross their fingers. A picture of crossed fingers is an emoji available in most sets of emojis. Here's a picture. https://tinyurl.com/w3zgzw7 There is one other meaning, rather odd. There is a tradition that it is OK to make a false promise if you have your fingers crossed behind your back (that is, hidden).

To wish good luck. https://www.google.com/amp/s/dictionary.cambridge.org/amp/english/keep-your-fingers-crossed

Hi In this sentence it means Let's hope/we hope that is not the case . I keep my fingers crossed means good luck

It means Good luck

Expecting good or desirable result from something