We know Manchester United has only brought in two new players so far it is too early to say they can not finish in top four. New manager Ruben Amorim is great strategist who can improve team. Current players like Bruno Fernandes and Marcus Rashford are still very talented and they can become more consistent under his leadership. But finishing in top four is tough goal it is not impossible with new coach and strong team especially since there is still time to sign more players
Yes, especially Rashford under Amorim looks very good! 
If you didn't know, Rashford had a conflict with Amorim from the first days when Amorim became the manager of Manchester United, all last season Rashford was on loan at Aston Villa, and now he plays in Barcelona. I don't know what top 4 you are talking about, it seems to me that in the current state Manchester United is not capable of achieving such goals, for this very big changes are needed.