Copying from an application like Microsoft Word also copies underlying information like formatting and other information.
This information does not translate well in other applications like uEducateUs.
The best solution is to paste as “unformatted” text.
Copy from the source application by selecting the text and CTRL+C (or Edit > Copy)
Right-click in uEducateUs and choose Paste as plain text
You’ll need to reformat the content in uEducateUs, but the result will be as you intend.