Complex sentence: As of March, Turkey-backed FSA and the Turkish army were effectively blocked from moving further east by advances of the SAA, towards their next goal of capturing the SDF-held city on Manbij, and assisting in the attack on Raqqa.
Split into simpler sentences: As of March, Turkey-backed FSA and the Turkish army were effectively blocked from moving further east by advances of the SAA. Their planned next goals were capturing the SDF-held city of Manbij, and assisting in the attack on Raqqa.