mac book os big sur version 11.7.11 How to download google chrome,

Correct. Google has now ended Chrome support for macOS 11 or lower.

System Requirements

• Minimum macOS: macOS 13 (Ventura) is required for Chrome version 151 and newer.
• Older macOS 12 (Monterey): Chrome 150 is the final version to support macOS 12.
• Older macOS 11 (Big Sur) and below: No longer supported for updates.

Sorry, time marches on and macOS 11 Big Sur is now obsolete. Most third party software no longer supports it.

You might consider the Firefox browser as it it idled as still supporting macOS 11. From a security standpoint you are taking a substantial risk by using old software and browsers known to have security flaws.

Firefox v156.0.1 (current) supports macOS Catalina 10.15 or later. This is bound to change.

The Brave Browser (1.96.59), since it is based on Chrome, requires macOS Ventura (13.*) or later.

Increasingly, third-party vendors are moving away from older, Apple unsupported operating systems of which Big Sur is representative.

Brave maintains a library of archived versions that will run under Big Sur. Write back if you need help finding them.

Write back if you need help finding them.

Here you go: https://support.brave.app/hc/en-us/articles/18347246446733-Changes-to-macOS-desktop-browser-requirements

Be sure to read it first.

Click the link for 1.80.125