Can I upgrade my ram?

So, the only way the RAM can be upgraded is with an AASP.

Please read this from Install memory in an iMac - Apple Support.

Memory is not removable by users on iMac (21.5-inch, Late 2012), iMac (21.5-inch, Late 2013), iMac (21.5-inch, Mid 2014), iMac (21.5-inch, 2017), iMac (Retina 4K, 21.5-inch, 2017), and iMac (Retina 4K, 21.5-inch, 2019). If the memory in one of these computers needs repair service, contact an Apple Retail Store or Apple Authorized Service Provider. If you’d like to upgrade the memory in one of these models, an Apple Authorized Service Provider can help. Before you schedule an appointment, confirm that the specific Apple Authorized Service Provider offers memory upgrade services.

So, you need an AASP. Find one here: Apple - Find Locations.

However, a RAM upgrade might not help much, since you claim the issue is that the processor isn't powerful enough.

Cheers,

Jack

Why do you want to upgrade the RAM? Are you having performance issues? If so, I believe we need to proceed with an EtreCheck report. EtreCheck is a useful App to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

Cheers,

Jack

Please post the EtreCheck report. Run EtreCheck, share the report to the clipboard, then open a new reply here and press the button that looks like a printed page to get a text input box big enough to paste the hardware and software configuration report here. This report has substantially more detail than what’s been posted, detail which might provide some insight into the slowness. Without some idea of the issues here, replacing parts may or may not help. The cause might be near-capacity storage, or to little memory, or installed software, or some other issue, for instance.

What year is your Mac?

Please also generate the EtreCheck report.

What type of hard drive do you have? (Hard Drive, Fusion Drive, SSD)

What would you use a 2TB drive for?