The winger has penned a deal to 2030.
“It means a lot for me because I love this club. Every time I pull on the jersey, I'm so proud,” he told MUTV.
“Every time I'm on the pitch, I want to fight for this club, and I'm so happy to be here for a long time.
“First thing, you have to believe. I will always believe in myself.
“I work very hard to achieve a lot of things with this club. Today, I'm so happy to extend for five more years.
“I want to be here for a long, long, long time. Not just five more years, but maybe for all my life.”
On manager Ruben Amorim's system, Amad also said: “Yeah, we learn every day. We learn, you know, it's a new system for everyone. At the beginning it was not easy, but I think now the team is starting to understand the system a little bit more.
“The manager and the staff are, every day, at the training ground to help us, to understand more of the system.
“We are very happy to have them and we want to follow them for the system, because we know at the end we will have success.”