The 29-year-old joined Arsenal in August 2011 but initially struggled to adapt to the pace of the Premier League.
However, the Germany international is now showing his best form, having struck up a solid partnership with Laurent Koscielny.
Arsenal kept their ninth clean sheet of the season on Tuesday in a 2-0 win over Marseille in the UEFA Champions League, and a contented Mertesacker is hoping ongoing contract talks can bring a positive outcome.
"I am very happy here," he said. "The first year was tough for me, a very tough challenge, but the club and the manager always trusted me in a special way.
"I got a big injury in my first year, so I took my time to settle down completely and there were a lot of reasons.
"I think it is a little reward that we are talking (about a new contract), because I still have one-and-a-half years left. There is no rush but it seems that some people are delighted with my performances at the moment. I am pleased with the situation.
"It took me a while to get to that level. But the manager always trusted me and said I was intelligent enough to cope with problems."
Arsenal have benefited from Mertesacker's upturn in form and currently top the Premier League table.
