High resoluted photos show worse in timeline

I have a problem with the quality of photos in my timeline. I have high resoluted png files (2480 x 3507 and 60 p). When I watch them in my preview window they are fine and in high quality. When I draw them into my timeline the image turns into 24p and gets blurry and unsharp.I tried already with proxy and optimized quality while importing and wether its gets worse (proxy) or not better. Please what can I do?Its also not a performance problem, because when I render the clip with 1080p, the image quality stays bad in the final clip.Where is the problem? Can please somebody help me?Thank you so much!

Something in the PNG encoding could be throwing things for a loop. Save the file as JPG or TIFF format and give that a try.
Beefy files are more favorable for video but the same doesn't always hold true for image files translated into video.
(I've never had a problem with JPG looking funky in the timeline.)