Donnarumma quality as the best goalkeeper cannot be doubted, after successfully breaking through the number one goalkeeper in the italian squad, he will do it again in the PSG squad, he is still very young and the quality of his reflexes is very good when repelling the opponent attack. If PSG coach Pochettino gives Donnarumma playing minutes, he will easily shift keylor navas in the PSG main squad, Moreover, the presence of Donnarumma in the PSG squad is projected to replace the position of Keylor Navas who has entered his old age.
Keylor Navas will be like Buffon in Juventus who plays with experience. Years ago, Szczęsny joined Juventus from AS Roma but he had to accept the second position, after Buffon. Then gradually, he took the first position and is the main goalkeeper in Juventus after that. PSG has solid plan with Donnarumma. They signed a long contract with him, to prepare for Keylor Navass' decreasing performance, retirement or leave in next 1 to 2 seasons.
Even now, it is hard to say who is a better goalkeeper between them but Donna has to accept the second position because he only joined the club in this summer.
Messi isn't going to be able to score as he will be at his national team in a match one day before the Ligue 1 match. And Neymar won't also. Because the World Cup Qualifier matches are going to end on that day rather than an earlier date. We will most probably watch Messi and Neymar as of the CL matches. And it is only in one week so we will not have to wait for a long time.
They will be given rest by PSG. They can win match without Messi and Neymar. They need them for big matches in Ligue 1 and Champions League and they are smart enough to give those important players good time to recharge energy after long flights and international duties.