Contributing

I want to contribute code to Lichess Mobile

Set up your development environment;
You may want to install a local instance of lila, see lila wiki for that;
check the wiki for more documentation
Pick a GitHub issue to work on. The good first issue and help wanted tags are useful;
don't edit manually the app_en.arb file! See about internationalization in the wiki.
Communicate with other devs on Discord.

I want to report a bug or a problem about Lichess Mobile

Make an issue. Before creating an issue, make sure that:

You list the steps to reproduce the problem to show that other users may experience it as well, if the issue is not self-descriptive.
Search to make sure it isn't a duplicate. The advanced search syntax may come in handy.
It is not a trivial problem or demands unrealistic dev time to fix. Such issues may be closed.
You're not posting a one liner such as "X feature is missing". It is useless, we already know exactly what features are missing. Feature request are allowed if you're suggesting a new idea, while explaining it in the most detailed and clear possible way.
You provide device hardware and operating system information to help with the debug.

I want to suggest a feature for Lichess

See that guide.

I want to help translate Lichess

Check out Lichess on crowdin.com.

Other ways to contribute

Also see https://lichess.org/help/contribute.