Galaxy Tab Pro 10.1 SM-T520 Touch Screen Digitizer Replacement Unsuccessful! Неудачная ?

I had Galaxy Tab Pro 10.1 SM-T520. Touch screen was broken so I watched many videos here on youtube how to replace it. I bought new replacement part. Everything was ready. But when I started to heat up the sides of touch screen to remove double side tape which holds the digitizer I was frustrated. Some kind of glue held all touch screen surface everywhere. So when I finally got rid of the touch screen the view was horrible. ALL surface was covered with some glue!!! I haven’t seen that in any other video instruction! It’s a disaster. Can somebody tell me what was wrong???