But Bottas told Finnish media he intends to step up in 2018.
"I did not realise a year ago how much there would be to learn," he is quoted by MTV.
The 28-year-old said he had a good winter break but he is now back at work.
"I have been in the factory a couple of times and worked on the simulator," Bottas revealed. "The team has done well.
"It always depends on what the other teams have done as well, but we believe that our car is better than last year.
"There is one goal for the season: to fight for the championship. I know all the people now and how it all works," he said.
He also told Ilta Sanomat newspaper: "Perhaps one of the biggest changes is my driving position. Last year I fought all season with it but now I could achieve a decent driving position."
As for the future, Bottas wants a new deal and Mercedes is negotiating with Lewis Hamilton about a contract beyond 2018.
"For me it's good for Lewis to continue. I clicked well with him and he's a quick driver and a challenge," he said.
And for himself, Bottas explained: "The best contract argument is to win as many races as possible."