In July 2016 started the longest shutdown period in GSI-history. Besides the extensive maintenance and upgrade measures, the main work package is the civil construction project GAF (GSI Anbindung an FAIR, Link of GSI to FAIR) which comprises additional shielding of SIS18, fire protection measures, as well as the connection of the new beam line between FAIR and the existing GSI facility. At the UNILAC the modernization of the post stripper RF system and the refurbishment of the HVAC system (Heating, Ventilation and Air Conditioning) have been started. In addition to these measures, the complete control system stack for SIS18, ESR and the HEST will be replaced by the FAIR system. Presently all accelerators are far from being operational (except the Cryring). Nevertheless we decided to provide a comprehensive user beam time already in 2018. During the shutdown we follow a detailed and ambitious schedule to bring our accelerator facility back online in time. The challenges and our re-commissioning strategy will be presented in this talk.