@monika I help to coordinate the translations for DHIS2, and @phil asked me to respond to you. As Phil mentions, we have a few challenges with the current translation workflow, however, it will work. To get you started, we will need to make a few changes to the core source code, but I can take care of that.
The easiest way probably is to use the online translation service which we have here (https://translate.dhis2.org) You and your translation team can sign up for an account there after. I would suggest that you start [here] (https://translate.dhis2.org/uk/dhis2-core/translate/dhis-2/dhis-services/dhis-service-core/src/main/resources/uk.po#filter=incomplete) . These are the core translations on the Java server. After that, there are quite a few apps which need to be translated. I can add those in due course, but its usually good to get started with the core translations first.
After you have finished that piece, please let me know and I can sync that with the source code for DHIS2.
Are there any apps in particular you are interested in translating? I would probably suggest to start with data entry and the pivot table app, since many users tend to use those apps, but it will depend a bit on your circumstance.
If you have any questions, feel free to ask.