Make background colors transparent in a special way

[dgoelid]

Dear community,

how can i make my background transparent in that way like shown in the picture?

Thank you for your help.

[rich2005]

You need to give more information.

Do you mean the tee shirt logo and the white colour ?

   

Usually when printing there is no white. The printer uses Cyan / Magenta / Yellow and K (Black)  There is no white ink.  Anything white takes the colour of the material. No need to make it transparent. Make your logo in Gimp. Send to the printing company.

That logo however is only 3 colours black, yellow and white. 
My guess is it is screen-printed see: https://www.customplanet.co.uk/what-is-s...step-guide and the section 'What is the difference between screen printing and digital painting.

That logo would use the 3 'spot' colours and built up in 3 layers, one screen (stencil) per layer, and producing the screens is a whole different process.

[rich2005]

Is it a football club logo ? I can not find that one but as an example. this:

   

Use Colours -> Color-to-Alpha and what ever colour specified, white is default, becomes transparency. Transparency is depicted in Gimp as a checker pattern. Export your image as a png file to preserve transparency.