I think keeping up with Liverpool's performance for next season is upto Klopp to figure it out. Mane and Sallah will be a big loss to the club but the too have to move on. Their performance in the last season was second to none but at the same time Liverpool can still do better without them it is just for Klopp to figure out how.
I agree that although it is certain that Mane will leave Liverpool, it is very likely that Klopp will be able to find players who can replace Mane because so far if we look at some of Klopp's purchases of players almost all of them have proven effective, such as the purchase of Thiago, Jota, Luis Diaz and Konate although bought at a price that is not too expensive but under Klopp's guidance they were able to play brilliantly.