how can i update my os x yosemite version 10.10.5

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there.

With the above information in-hand - follow this How to get old versions of macOS and verify what version this computer Qualifies to install.  For Best results use Safari to commence the download as Others may not work.

Make Time Machine Backup  is very useful and can be used to Revert to Previous Working macOS

Notation - Mojave is the Last version to support 32 bit applications / extensions and Drivers. Catalina & Big Sur supports only 64 bit and there is no workaround.

Suggest using Go64 to find 32 bit application before attempting the upGrade. Some or many of the Application already installed may required update or upGrades to 64 Bit Versions.

Are there any AntiVirus, Disk Cleaner, Optimizers, Un-installers, etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS and may even Corrupt the OS requiring a Reinstallation

Apple removes the last macOS version when the new update is released.

Because of problems with High Sierra, you can still download Sierra from Apple.

You will need to find someone with a copy of El Capitan. If you had downloaded it and not installed it, you would find it in iTunes Purchased tab.

Downloading each installer and saving it, is what the savvy Mac user has done for years.

Maybe even creating a bootable USB drive installer.

Backup your hard drive B4 running an upgrade.

Thanks