The newly-promoted side have agreed to sign Orel Mangala, who is set to become their 12th summer signing.
The 24-year-old will have his Forest medical on Tuesday with the deal set to take Forest's summer spending to £73.5 million.
The Belgian international scored one goal in 29 appearances for the German side.
In March, he made his Belgium debut.
A deal to sign Real Betis left-back Alex Moreno is still being worked on by Forest.
The contract of the 29-year-old is up in five years.
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As they prepare for their first season in the premier league in 23 years, Forest have been busy in the transfer market
Steve Cooper's side is set to get a new player after Jesse Lingard's arrival.
Lingard is Forest's highest earner, with his deal thought to be worth $115,000 per week plus incentives.
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Lewis O'Brien and Harry Toffolo are Forest new additions.
Last month, Forest signed Nigeria forward Taiwo Awoniyi for a club-record $17.5m fee and also brought in two other players in deals worth over 17 million dollars.
Brandon and Giulian Biancone were signed by Forest.
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The Reds will play their first game back in the top flight on August 6th when they travel to take on Newcastle.
After winning the Championship play-off final at the end of May, Steve Cooper's side were promoted to England's top tier.
Sky Sports will show the West Ham game at the City Ground on August 14.
The next few games for Forest will be difficult, including a trip to Manchester City before the end of August.
The two teams will play each other at the King Power Stadium on October 1st and the City Ground on January 14th. They will travel to Manchester United on Boxing Day.
The final game of the season for the Reds will be a trip to Crystal Palace at Selhurst Park, after they played host to Arsenal.
The transfer window will close at 11pm on September 1st.
Sky Sports has a dedicated Transfer Centre website where you can keep up-to-date with all the latest news. Sky Sports News gives you the ins, outs and analysis of sports.