In 2004 Manneh started training at the Rush Soccer Academy, a United States soccer franchise for children and youth in Bakau.[2][3]
At the age of 17 he fled the dictatorship in his home country Gambia reaching Bremen and living in the refugee camp of Lesum.[3][4] Following a trial he joined the Blumenthaler SV U-18 team before playing for the U-19 side in the youth regional league, the second-tier youth league in Germany, where he scored 15 goals in 11 matches. These performances earned him trials with FC St. Pauli, Hamburg, Schalke 04 and Wolfsburg.[3][4]
Having chosen to stay in Bremen and play for Werder Bremen, Manneh initially played for the club's youth team.[2] On 10 March 2015, he signed a three-year contract with the club running until summer 2018.[3][4]
On 25 July 2015, he made his 3. Liga debut for the reserves against Hansa Rostock scoring the winning goal in a 1–2 away win.[5] Four days later, he made his first appearance for the first team; having entered the pitch after 60 minutes he scored four goals in 15 minutes in a 7–0 friendly match win against SV Wilhelmshaven.[3][6]
After scoring and assisting two goals each in his first seven appearances for the reserves in the 2016–17 season, Manneh made his full Bundesliga debut on 21 September 2016 in a 1–2 home defeat to Mainz 05 before being replaced by Lennart Thy in the 55th minute.[3][7][8] He also started in the following match three days later, a 2–1 win against VfL Wolfsburg, Werder Bremen's first victory of the season, being substituted off after 73 minutes.[3]
Manneh scored his first Bundesliga goal on 15 October, in Werder Bremen's 2–1 win against Bayer Leverkusen.[9]
He made his return from a 21-month injury layoff 8 December 2019, coming on as a substitute for Werder Bremen II.[10]
Manneh was released by Werder Bremen when his contract expired in summer 2020.[11]