I have a Mac OS Sierra.
I have a 2011 Mac macOS Sierra 10.12.6. Can I update it any more? Please send me an Update if possible or what do I need to do? thank you!
iMac 21.5″, macOS 10.12
Question marked as
You can upgrade it to High Sierra but not beyond that. See the following from Identify your iMac model - Apple Support
iMac (21.5-inch, Mid 2011)
Model Identifier: iMac12,1
Part Number: MC309xx/A, MC812xx/A
Latest compatible operating system: macOS High Sierra 10.13.6
See instructions in: How to download macOS - Apple Support
You should also use the current version of a 3rd party browser such as Chrome or Firefox since you will not be able to use the current version of Safari with High Sierra.