When editing links, it’s very important that you don’t completely delete the link text before typing your text in. Doing this will delete the entire link tag along with all its special styling.
Instead, carefully select all the text except the first and last characters. Type your new text between these two characters, and then as a final step, go back and delete them off each end.
Then place your cursor anywhere in the text that you have just typed and click the Hyperlinks tab in the sidebar. Adjust your link settings and press Save.