I'd like to send some btc, but it's saying that it can't estimate the fees at the moment, and that i have to activate the fallbackfee, or that i wait fews blocks..
To activate
fallbackfee you can either start your wallet with the
-fallbackfee=value parameter or add
fallbackfee=value to your bitcoin.conf file.
The value you set will be used by default and it has to be in Kb/btc.