My seed from Electrum has 12 + 2 extension words. Iconomi ask for 12 My seed from Electrum has 12 + 2 extension words. Iconomi ask for 12, 18 or so. How can i do to claim my BTG?
Any way to convert 12+2 seed to bip39?
Unfortunately Coinomi uses BIP32/BIP44, those are not compatible with Electrum seed. What you need to do in order to retrieve your BTG:    


Move your BTC to a new wallet, so they stay secure and safe.  
Make a new wallet with Coinomi.  
Use the sweep function to sweep private keys from your old BTC wallet.   
Shouldn't be that many private keys needed to sweep, usually 1 - 3 that hold BTG.  
Or you can check on block explorer before sweeping.