Can I use the quick link from my old shimano chain to my new shimano chain? Or the old link will cause any problem? I have to say that no damage is visible in that old quick link. Both 2x11, same model.
If I understand correctly you want to buy a new chain and re-use your previous masterlink. I'd strongly advise against.
The reason for NOT re-using an old masterlink with a new chain makes sense. Chains are commonly replaced because they are worn. The links are lengthened with time and above a 1% lengthening the chain is considered over the top. The masterlink is worn at the same rate. Now if you use an old masterlink on a new chain you'll have ~110 links of the correct length and one that is longer. The smallest annoyance may residde in a noisy drivetrain. The worst will have the chain skip at each time it reaches the sprockets and once again it reaches the rings.
Shimano's advice is to use a fresh joining pin every time. Ideally you would press out a different rivet, and not use the same hole that the earlier joining pin was pressed into.
Other brands like KMC and Wipperman etc offer master links, which can be reused effectively provided they clip together okay.
Always carry a spare master link in your tool kit!
Shimano says do not re-use Quick Links.
Do not reuse a QUICK-LINK that has been removed. If the QUICK-LINK is reused, there is a risk that it will loosen and become detached, which may result in an accident.
KMC says the same (about 10 and 11 speed chain versions)
The Missing Link on chain models X11SL and X11L can not be reused. All other Missing Links can be reused between 2-3 times per life cycle of the chain. If you purchase a replacement chain, the used Missing Link should not be reused and is not interchangeable. Missing Links offer riders ease of maintenance and quick chain replacement when there is an emergency on the road or trail.
SRAM 10 and 11 speed PowerLock links should not be re-used either.