Medisana is a special situation. There is an offer for €2.80 per share and the shares are trading around €2.70. These offers under the German law WPÜG are normally quite safe. Financing is safe because the cash is on a bank account at BHF bank. Caveat is that this is a Chinese bidder and volume is low.
As always do your own research. Original binding document is in German, only translation of the offer document is available in English.