Can I download from my bank last years (2019) statement?

You can select the period as required and download any statements from QB

That is a question for your bank. If you can then you will be able to import all the data but be careful with dates and do not overlap already synced transactions or they will double up

I lost all my data for 2019 and 2020 

can I have my bank download those years

I'll make sure you can download your prior year's bank statements, CD1616.

While the system only downloads up to the last 90 days of transactions, you can manually import data beyond the time limit. Download the bank statement from your bank using the following supported formats or file types:

• Comma-Separated Values (CSV)
• Quicken (QFX)
• QuickBooks Online (QBO)
• Microsoft Money (OFX)

Once the bank file is ready, start importing the file to your QuickBooks Online company by following these steps:

1. Go to the Banking menu and select Banking.
2. Choose File upload from the Update drop-down. You can also select Upload transactions manually.
3. Hit Browse and pick the downloaded file.
4. Select Next.
5. From the QuickBooks account drop-down list, choose the account to which to upload the bank transactions, and select Next.
6. If you're using a CSV file, follow the prompt to select columns from the CSV file that match QuickBooks Online banking fields. Another option is through the Import Data page. To do so, click the Gear icon, select Import Data, then hit Bank Data.
7. Click Next.
8. Select Let's go! or Finish.

I've attached here an article to guide you with the process: Manually upload transactions into QuickBooks Online

If you have additional questions about the process, keep me posted by leaving me a comment. I'd be glad to assist you further. Have a good one.