You may want to use Google Analytics’ Goals and Event Tracking features. A goal could allow you to monitor when users reach a ‘Thank You For Contacting Us’ page, indicating they have completed the contact form. First, set up a goal in your Google Analytics admin panel, then define the details. If your contact form redirects to a thank you page, you can use Destination type goal. You need to input the URL of the thank you page in the “Destination equals to” field.
However, if your page does not redirect to a new page and only posts a message, you may need a bit more technical setup using Event Tracking. This will require you to add additional code (JavaScript) to your website, particularly in your contact form completion trigger. You will use the ‘ga.send’ method to send an event when your form is submitted. Once the goal is set up, wait for data to be collected then use the Conversion reports to track conversions.
As for URLs with UTM or topic parameters, these won’t interfere with tracking. UTMs are designed to help tracking in Google Analytics and won’t affect your form submission tracking unless you’re explicitly setting them to. Similarly, ‘Topics’ or other URL parameters shouldn’t interfere with your goal or event tracking, as long as your goals and events are set up to match the core URL and not take into account the varying parameters.