The lack of specifics to your question make it impossible to help you so I can only answer with the same vague generalities in which the question was asked. Basic signs of product market fit:

High CTR on ad spend: if you're seeing above .3 Unique CTR on your ads, that's a good sign that people are interested in what you're offering.

High conversions on landing page or install:
On a web page, a general first funnel conversion of something with traction will be 20% or above. For a mobile app, it will be account activation of 35% or more.

Next comes user love. User love is expressed many ways. Engagement is most obvious but in early days, non-incentivized social shares are a promising sign. So too are customer feedback messages with praise and thanks.

Happy to talk to you in a call about what you're doing.