Fred became Mourinho's second-signing for the club when he joined from Shakhtar Donetsk for £52m in the summer of 2018.
However, the Brazilian struggled to live up to his large fee in his debut season and under Mourinho, he only made eight appearances in the Premier League before the Portuguese coach was sacked in December 2018.
Fred believes that while his debut season at Old Trafford was "very difficult" with on and off-field issues playing a part in poor form. However, he also revealed that he is now "very settled" at the club.
"I believe the first season was very difficult for me," Fred told Sky Sports. "There was the process of settling down here, but also other personal things that were happening in my life, such as the birth of my son.
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United were on a run of 11 games undefeated when football was suspended and while it is unclear when "Project Restart" will take place, Fred is hopeful training will resume at the club's Carrington complex next week.
"In the past weeks the squad has been joining online for official sessions," he said.
"So everyone is there, including the manager, fitness coaches and other assistants, so we are in contact with the manager.
"I believe some of the players will be able to go to the training ground next week. Perhaps we can resume ball training in two weeks' time.
"Slowly we will try to get back together. That would be very important for everyone."