In the 2007/08 season, he was included in Dynamo's application three times for the matches of the higher league, but he never appeared on the field in the championship matches. Instead, in September 2007, he came on as a substitute instead of Ayla Yussuf in a friendly meeting for the club's 80th anniversary against the Italian Milan (2:2). After the match, Milan president Adriano Galliani praised his performance. In an official match for Dynamo, Garmash made his debut on October 31, 2007 in a cup match against Simferopol's "IgroService" (4:1). He made his debut in the top league as part of the main team of "Dynamo" on August 31, 2009 in a game against "Metalurg" Donetsk (3:1).

In January 2020, he was loaned to the Turkish Rizespor for a six-month loan. On January 27, 2020, he scored his debut goal in the Turkish championship. In total, by the end of the season, he played 16 games for the club and scored 3 goals, and in August he returned to Dynamo. After returning from Turkey, he maintained his form with Dynamo, but the club did not include him in the application. The team photo session before the season also took place without Denis, however, on the last day of the transfer window on October 6, Garmash was included in Kyiv's application for the 2020/21 season of the Ukrainian Premier League. The 30-year-old player received the 19th number