The Sweden defender made his 10th appearance for the Parkhead side in the 3-0 win over Ross County on Saturday and revealed he is feeling more comfortable with every passing game after some initial shaky displays.
"I feel like I have more to give. I feel like it’s getting better," Starfelt said.
"I feel more secure for every game. I just need to keep working hard and hopefully I will only grow.
"Of course I know, I have played football for a long time and I know you will have difficult moments. But then every player will have difficult moments.
"You’ve got to just push through them mentally and if you keep working hard it will turn around and that’s what I’m trying to do.
"I try to work hard every day and keep my confidence up and that’s what my focus is on."
It was a change of defensive partner for Starfelt with Stephen Welsh dropping to the bench after captaining Scotland Under 21s in midweek.
"Cam came in for the game against Ross County and did a very good job," Starfelt said.
"Of course it’s optimum to have played with your centre-back partner before. It felt like it was easy to play with him. I felt that with the others too though.
"When you change a lot of players it becomes difficult but when one or two come in it’s easier to adapt when you have a strong core.
"Everyone who has played there has done very well and they’ve been easy to play with.
"But of course the more you play with someone the more you get to know them and the more you can adapt to each other.
“So it will get better also."
Starfelt revealed he will brush up on Celtic's history ahead of the trip to Seville on Thursday but insists Ange Postecoglou's approach can bring a positive result.
"It’s a very big game there. There are tough games in a tough group," he said.
"But they will also be fun games so we’ll go and play our football and see where it takes us.
"It will be my first time playing in Seville. I haven’t talked too much about [Celtic's history in Seville] actually but now you’ve told me I will look into it some more!
"I feel like we have a very clear way of playing and the coach is very clear in how he wants us to play.
"So everyone knows what we want to do. We will go and perform our best and see how far it will take us.
"We know it’s going to be very tough but we also believe in ourselves so we will see.
"It’s important how we want to play this game, what we want to do on the pitch.
"It’s the first game in the group, it’s obviously a very tough game so we will go and try to win and play our football and see where it takes us."