Hi @Mossab 

To create a UML Class Diagram in Lucidchart, start by opening a new diagram.

Select the UML Class shapes from the shape library and drag and drop them onto the canvas to represent each main class.

Double-click on each class to add attributes and methods. Use the line tool to establish relationships between classes, and customize the connections by adding arrow types and labels to clarify their nature.

Enhance your diagram's readability by utilizing Lucidchart's formatting options to color-code or style elements. Finally, add a descriptive title, such as "Ticket Event System Class Diagram," to complete your diagram

Refer some help articles and make use of some preferred templates.

Tickets class diagram example | Lucidchart

Diagrams and Tutorials | Lucidchart Learning Center

Hope this helps - Happy to help further!!
Thank you very much and have a great one!
Warm regards