The Selecao saw Egypt score twice in the second-half to reduce the deficit to just one goal after they headed into half-time with an impressive 3-0 lead.
"It is always hard to debut in a competition like this," Oscar told Goal.com after the game. "We had a great first-half.
"In the second-half, we were a bit careless. We entered the pitch a bit more relaxed and we allowed them to grow in the game.
"They also came up with a different strategy, which made things harder for us, but we secured the three points.
"We made some mistakes which we cannot make. We have to improve this. Our team is growing after every game.
"My performance was good as I picked up two assists. I did what I usually do on the pitch and I tried to help my team as much as possible. I hope that I will continue like this."
Ganso, who came on as a second-half substitute, is hopeful that he will play an important role at the Olympics and was full of praise for Oscar, who replaced him in the starting line-up.
"The opportunities will come," he noted. "I have to be ready to give my best for the team.
"Oscar is a very intelligent player. Tactically speaking, we played as two attacking midfielders who get close to the strikers."