Ago = до настоящего момента
Last time I had anything from her
was a couple of weeks ago
Before = до определенного момента
We will finish before he arrives
After = после определенного момента
We will finish after he comes
Until/till = до того времени, как
We waited until he finished his homework
By the time = к тому времени как (одно действие завершится к тому времени, как произойдет другое)
By the time he finished, I had cooked dinner
When = когда
We‘ll go to lunch when you come to visit
By = к (какому-то моменту)
I will inform you about my decision by Monday
During + существительное = в течение, на протяжении
I’ve taken lots of interesting photos during my trip to Mexico
While/as + придаточное предложение (с подлежащим и сказуемым) = в то время как
She began cooking while I was finishing my homework