Though it seems hard to believe, USCIS offers no way to check on the progress of an individual case once it is filed. Estimates of processing time are extremely vague and unreliable to the point of uselessness. Further, we are in an unprecedented situation as far as the COVID-19 pandemic and its effect on processing times. The change in presidential administration going into 2021 also makes any attempted guess at processing time useless. For these reasons, we are unfortunately unable to answer any questions about how long it will take to get to the next step or the end of your case.
There are two things you can do, though they are of limited use.
You can go to https://egov.uscis.gov/casestatus/landing.do and enter the Receipt Number from your USCIS Receipt (labeled as Form I-797). However, all this does is confirm that your case has been received and is pending. That "status" will stay exactly the same until the day or a few days before a decision or interview notice is sent out. Therefore, you cannot really learn anything at all useful about your case except to be reassured that it has not disappeared.
Secondly, you can go to https://egov.uscis.gov/processing-times/ for information about average processing times, keeping in mind that these estimates are famously inaccurate. On that page, you input your form number (look at your Form I-797 Receipt Notice and it will tell you what kind of form you filed). You also input the Field Office or Service Center that has your case, which you also learn by looking at your Form I-797 Receipt Notice in the lower left corner. Then click the Get Processing Times button to reach a page that estimates how many months your case might take at a minimum. Most of these numbers are actually far higher than the reality. They do this so that we will not be able to complain that the case is late because they are almost always able to say that your wait is still under the supposed average.
One other piece of information on this page is the "Receipt date for a case inquiry." This means that unless your case was filed before that date, we do not have the ability to even ask USCIS why the case is taking so long. They literally will not accept a call on the case and will not even log the inquiry as having taken place. For example, if the "Receipt date for a case inquiry" is July 1, 2019, we cannot even inquire about any cases filed after July 1, 2019 because they are still "too recent" according to USCIS. If your "Receipt date for a case inquiry" is not yet current, we appreciate your not asking us for an update on the case since the answer will invariably be that we do not have and cannot get one.
Hopefully, these resources will help you feel more connected to your case. But the stressful reality is that once we have a receipt, there is no real interaction with or communication with USCIS about the status until virtually the moment that the next step is upon us.