You say I download the entire program again or download Debug. Log
Debug.Log size: 1.550 KB
The debug log tells you wants going on. What I'm saying is if you tried to run what you have again and it still doesn't work and you are sure there is sufficient space then you can try a different version in the link provided at Crypto-city.
What should I keep in order not to lose the coins?
Always make a backup of your wallet.dat and put it some place safe (usb stick for example). This is the file that contains your private key. Delete everything, except for your wallet.dat and run the wallet executable.
If it's not connecting, make sure the wallet is shutdown. Create a grandcoin.conf file in the same directory as wallet.dat and add the following and save it:
addnode=149.56.183.177:12377
addnode=80.188.248.200:12377
addnode=185.8.166.94:12377
https://www.crypto-city.com