Hi
Don't be mislead. Office 2011 DOES work in all current versions of Mac OS X up to and including all versions of High Sierra 10.13 issued to date.
Office 2011 works on all versions of Mac OS that it was designed to work on plus some new ones.
Your license of 2011 is perpetual. It never expires. Your product will work until Apple changes Mac OS X. As long as you don't install an unsupported version of Mac OS, Office 2011 will run forever.
Office for Mac 2011 system requirements
Office 2011 is 32-bit and will never be 64-bit.
Office 2016 started off as 32-bit and was upgraded to 64-bit in an update.
Office 2019 will be 64-bit
Each product has published system requirements. As long as you don't try to run them in other configurations, they will work just fine.
You could have purchased an Office 365 subscription. The subscription option was offered before the end of life of Office 2011. If you had purchased 2011 by subscription, you would have received regular updates AND upgrades. Your install of Office would
now be 64-bit Office 2016. Those who took advantage of the Office 365 subscription got the upgrades. Those who did not, didn't. In hindsight, I think the subscription option was the better deal.