Please check first that it has not already been reported. Also consider enabling debug mode before reporting the issue so that you can provide as much details as possible to help fix it.
If possible, please provide a screenshot. A screenshot showing the problem is often more useful than a paragraph describing it as it can make it immediately clear what the issue is.
Again, please check that it has not already been requested. If it has, simply up-vote the issue - the ones with the most up-votes are likely to be implemented. Adding a "+1" comment does nothing.
If you want to add a new feature, consider asking about it before implementing it or checking existing discussions to make sure it is within the scope of the project. Of course you are free to create the pull request directly but it is not guaranteed it is going to be accepted.
Building the apps is relatively easy - please see the build instructions for more details.