Adobe Stock Images downloading took too long. 4.9mb file took almost

There are different reports on this. But they are rare (compared to the user base), and I would suspect more a problem with a local configuration than an Adobe issue. 

Check if the problem is also present, when you change the computer or the network. A high number of assets in the library could also cause problems. Some time ago, access to the libraries was slow, when you had more than 100 elements in the library.