There are three questions for Liverpool.
1. Can the front three, especially Salah, repeat last season? I think it will be very hard to do, as teams won't be caught by surprise any more. There is also a question about Salah's shoulder injury, which was said to be minor but clearly impacted him in the world cup.
2. Can they replace Coutinho, i.e. come up with a plan B? The scoring of the front three rather disguised what they lost without Coutinho. This was badly exposed in the CL final. They have spent in this area so it will largely depend on how the new guys do and if there is a clear tactical plan.
3. Have they fixed the defence? The signing of Van Dijk seems to have been a good first step and they now have the self-confessed best defender in the world returning from the world cup. The two fullbacks made a lot of progress last season and they have tried to address their dodgy goalkeepers. It looks like they have the players, but is the problem structural?