Hi @Omda4wady, thanks for reporting this! Please read https://www.mediawiki.org/wiki/How_to_report_a_bug and provide:

• a clear, full, complete list of exact steps to reproduce the situation, step by step, so that nobody needs to guess or interpret how you performed each step (currently there are no steps to reproduce, no clear and exact web address where to see a problem, what you click where after what, etc)
• what happens after performing these steps to reproduce,
• what you expected to happen instead,
• a full link to a web address where the issue can be seen,
• the web browser(s) and web browser version(s) that you tested.

You can edit the task description by clicking Edit Task. Ideally, a good description should allow any other person to follow these steps (without having to interpret steps) and see the same results. Problems that others can reproduce can get fixed faster. Thanks.

Also, when I go to https://en.wikipedia.org/wiki/Main_Page I do not see any option to collapse the side bar. On https://en.wikipedia.org/wiki/Special:Preferences#mw-prefsection-rendering , do you maybe have "Skin preferences > Use Legacy Vector" disabled? (Please always include complete steps.)