@piero90, Piero, remove the old glue/tape with a (little) heat and a plastic scrapper/credit card/fingernail, then use some 90% isopropyl alcohol and a lint-free cloth to clean the remaining adhesive. Use a good quality thin 2 sided tape to put back together, which you can find doing a google search/hobby shop/small electronics repair store when you figure which width would work for you. Links below show tear down of the Surface 2 and adhesive strips being applied. Check the attached links,instruction and guides, Good luck.
I hope this helped you out, if so let me know by pressing the helpful button.
http://www.techrepublic.com/pictures/cracking-open-the-microsoft-surface-2/75/
https://www.youtube.com/watch?v=Man6w3sdXMo