So you see, you can get tickets for 47 Euro (the cheapest variant) or for 100,34 Euro (the fastest). We have to say, the fastest variant is not really faster;) So just choose a middle variant in this case - 60,54 euro.
The travel time from Berlin to Lviv (direct bus) is 12 hours. So everything you find for more time - it's for sure time with a stop in Warsaw, Krakaw or other city in Poland. Also if you find buses for 19 hours (but there is no bus change, so looks like a direct bus) - it's also a bus, that makes stops in several cities in Poland, so for your ticket you get also a free Poland Bus Tour;)
Berlin is just an example, but it's one of the cheapest variants how to get to Lviv. You can also check the variants from your own city on the website. Or go to Berlin first and then take a bus to Lviv.