Complex sentence: He started competing as a senior with the reserve side FC Barcelona B, where he soon was joined by compatriot Ronnie Ekelund; during this period, he was frequently called up to train with the main squad.
Split into simpler sentences: He started competing as a senior with the reserve side FC Barcelona B, where he soon was joined by compatriot Ronnie Ekelund. During this period, he was frequently called up to train with the main squad.