You probably have a really slow internet speed of your 4G network, even it should be from 20Mbps to 50Mbps, and blockchain_headers file should be downloaded in less then a minute if Electrum is connected to good server. It is possible that your blockchain_headers file is somehow became corrupted during download, so if the problem continues it is best to close Electrum and delete that file (only that file), start Electrum and give it some time to sync again.