When you encounter a problem, then please read first the whole documentation in the Hatari source package and the information on this web site, this might help to clear some problems.
If your problem still then persists, you can either use the Hatari user mailing list to ask for help, or you can use the Hatari project forums. Optionally there is also a well-visited Hatari forum at www.atari-forum.com which is certainly worth a visit.
If you you found a bug, then please use the bug tracking tool on the Hatari project pages.
For other enhancements, there is also a section where you can post your patches there.
If you want to contribute to the Hatari development regularly, you should also join the Hatari development mailing list to discuss open issues, bugs and patches.