Complex sentence: During Markko's temporary return, he and Langston forgave each other and started to form a friendship but, however they were not successful in trying to get back together and Markko left town again and returned to UCLA, leaving Langston behind.
Split into simpler sentences: During Markko's temporary return, he and Langston forgive each other and start to form a friendship. However, they are not successful in trying to get back together, and Markko leaves town again for UCLA, leaving Langston behind.