We have a mobile app, with 3 million of downloads and 1.5 million of active users. This is a young product with the main market overseas. I just arrived to the company and I realized that they haven't done any user research before at all and they are creating more features in order to keep people using the app, since they leave after downloading it. These features then are not following any strong insight.
I think it's advisable to know our users obviously, so everyone is in the same page about them and we can create more meaningful features in the future and improve what we have in the app right now, that's what I think at least.
I can only think of two; one-on-one interviews and online surveys. From my understanding, interviews offer a deep understanding on needs and behaviours, but seems they fit more when a product is on its discovery stage, not live for 2 years already. As for surveys, they show how the people is using the app today, who they are, what they want, but it doesn't provide the whys and deeper understanding.
What kind of research we should go with? I guess the answer will largely depends on budget, time and our goals, also considering the fact that I'm the only one who takes care about ux at the company. Still, I would like to know the options so I can offer the one appropiate for our case.