Edoardo Mortara admits his first year with Mercedes in DTM was the "hardest" season of his career.
Mortara switched to Mercedes after six years with Audi, which saw him take the 2016 runner-up spot and finish inside the top five three other times.
However, the Italian's first year with Mercedes was of limited success, as he was only 14th in the standings, and only beat one of his five stablemates.
He particularly struggled with qualifying this year, as he was 14th or lower in 13 sessions.
"It was a very hard season. Maybe even the hardest of my career," Mortara told Motorsport.com.
"The car, the environment, everything is different. As a driver you have to completely change your driving style, it is very complicated.
"People do not realise how difficult this challenge of having to change and get used to things."
Mortara said he became "more and more competitive" during his season, which yielded only one podium at Norisring.
He ended the season on a high, as the Hockenheim finale was only the second round where he managed to score points in both races.
"I have become more and more competitive and was able to catch up on my teammates, I'm very happy about that," said Mortara.
"I had no expectations, I just tried to do my work. Nevertheless, we have found a way to improve during the last weekend of the season.
"When I arrived to Mercedes, they knew I would need some time to adjust. We have worked hard to improve ourselves. My driving style is quite different from the start of the season, and it's getting better and better.
"There is still a long way to go [to be back at the top]. At least I can see a light at the end of the tunnel."
It has yet to be confirmed whether Mortara will return to DTM next year, with the Italian joining the Venturi Formula E squad for season four.
However, Mortara said he would be keen to do a double campaign if the two calendars do not clash.
"If there are no overlaps in the two calendars, there is the possibility that I race in both series," he said.