Decha means plank, but also those are names of specific music notes: d e c h (it is b in english notation but here we use H for this sound) and a. We were thinking to make logo with those specific sounds showed on music staff (5 lines)
There should be 1-3 colors, if there will be more than 1 color logo should looking good in monochromatic also.
There should be name of company in logo - decha or DECHA and discription: teatr muzyczny or Teatr Muzyczny (it means Music Theatre)
We have an idea but it is just suggestion, that letters could have same height like those notes on a stuff. It will be nice to show in logo that people can expect something with music. 
Logo should look familiar and friendly
Thank you for the projects

Very good designer, fast working and making changes. Recomended 

Decha or decha or DECHA