They have good advantage in Premier League and not too big pressure from Arsenal with inconsistency of this competitor, but it's wrong to say Liverpool won't have to focus on their next matches in Premier League. Playing carelessly and losing like 2 matches can trigger their unbelievable and unimaginable collapse at the moment. Focusing and playing carefully each next match will be their best prevention of any collapse.
This is inseparable from the luck that Arsenal got in this round because they faced a much easier opponent compared to some teams who actually met fairly evenly matched opponents. That does not mean that Liverpool do not need to focus on the next match, but they have a slight advantage because they will face a much easier opponent. Especially after getting a win against PSG so Liverpool's burden will be much lighter.
Liverpool's next match will face Southampton and Everton in the Premier League so it will be a little easier for them to get full points because the opponents they face are not too strong and even Southampton itself is the weakest team in the Premier League at this time.