Complex sentence: Four days later, Kimmich made his first appearance in the UEFA Champions League in Bayern's tournament opener away at Olympiakos and he started in the Bundesliga for the first time three days thereafter, playing 90 minutes against SV Darmstadt 98 in a 3--0 win.
Split into simpler sentences: Four days later, he made his first appearance in the UEFA Champions League in Bayern's season opener away at Olympiakos. On 19 September, he started in the Bundesliga for the first time, playing 90 minutes against SV Darmstadt 98 in a 3--0 win.