will i lose my iMovie project if update and restart my computer

Hi, tijon66,

No, updates/upgrades do not cause loss of iMovie projects. Updating your iMovie within your present operating system should cause you no problem.

However, I see from your profile that you are using a pretty old operating system. If you upgrade to current Catalina, a 64bit system, then some legacy media (old video clips in certain formats) will not be playable in iMovie projects. So, that could cause you to lose your project because the legacy media will not play in it. If you intend to upgrade to Catalina then you should convert any incompatible legacy media to a compatible format before upgrading. When you open a library in iMovie you will get a notification of any legacy media files contained in the library and you will be given an option to convert. Also, in the File menu there will be an item called Check Media for Compatibility and that should give you a notification of files that you need to convert.

Here's a link that will give you more info about legacy media and what you need to do.

https://support.apple.com/en-au/HT209029

-- Rich