The German manager thanked fans in a message on his Twitter account.
The sportswear brand has agreed a minimum five-year deal from the 2020-21 season.
Scottish football chiefs set up sub-groups to make sure games restart at the 'appropriate time'.
Matthew McCombe, 21, disappeared in Amsterdam during the early hours of March 14.
With all games cancelled the players are spending their time delivering parcels to local pensioners.
The football authorities will have discussions with the Scottish Government next week about forthcoming games.
The club plans to close the upper tier of the Richard Donald stand for the 2020/21 season.
The near 30-year-old Celtic away shirt was taken from the National Football Museum in Manchester.