Why? my logo like this??

[Kinan Media]

Why my Header like this.....

 

[ItsMeRay]

It's too big, which is why it gets cut off.

 

[goodnatured kitty]

I had the same issue with mine, and I've probably adjusted the size a hundred times.

 

[UnboxingSve]

Channel art looks different on desktop, mobile, and TV displays — larger images may be cropped. For the best results on all devices, we recommend uploading one 2560 x 1440 px image.

• Minimum dimension for upload: 2048 x 1152 px.
• Minimum safe area for text and logos: 1546 x 423 px. Larger images may get cropped on certain views or devices.
• Maximum width: 2560 x 423 px. This means that the "safe area" is always visible regardless of screen size. The areas to each side of the channel art are visible or cropped depending on browser size.
• File size: 4MB or smaller.