

Мы поссорились, и с тех пор я его не видел.
We had a fight, and I haven't seen him since then.
Он переехал в Берлин и с тех пор не звонит.
He moved to Berlin and hasn't called since then.
С тех пор прошло уже пять лет.
Five years have already passed since then.
"с тех пор" is in the lesson "When" (Level 42), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,380 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.