The "broad" rules for Germany are like this:
1) you need to move your "point of interest in life" to Malta, the 183+ days rule is just a guideline and not cared about by the Finanzamt as the final "proof". That primarily involes:
- stay in Germany less than 183 days a year
- stay in Germany less than in any other country per year on a per day basis (the night counts, if you are in Germany 2am and leaving 5am the day counts as being in Germany, if you arrive 6am from Malta the day still counts as being in Mata)
- having NO apartment, keys to an apartment, owned property that is not fulltime rented out, room for your own discretion, clothing drawer etc in Germany in general no place that you have access to on your own will and can live in any time you like
- no stake in a Kapitalgesellschaft (everything besides sole tradership, self employment, that is registered in the chamber of commerce like gmbh, ag, etc pp)
- not married to a German living in Germany and especially not having kids with a German living in Germany ( that is game over - you can have kids being unmarried!)
- only visiting Germany on a temporary / leisure basis e.g. to visit family or for medical reasons (especially family visits are explicitly allowed without triggering a point of life conflict)
- cancel all local contracts etc pp although you could keep European things like European wide private health care coverage etc but be prepared for them to argue against that
- ditch German clients (this is something you have to talk about with your lawyer, German clients are fine, working exclusively for one is not etc pp but i am not expert here since i stayed clear of German clients in general)
- don't keep the majority of your money in German bank accounts (most will cancel your bank account anyways as soon as you deregister)
- deregister with city + finanzamt + change passport in Malta (deregistration form from your local city townhall needed)
- fulltime rent an apartment in Malta, don't do funky airbnb contracts etc pp while technically being fully legal the Finanzamt doesn't give a s**t about what is legal or not - they are scum and will use it against you
- proof your life in Malta with regular Instagram, Facebook, whatever posts / pictures and keep all local receipts for groceries, utilities etc pp
If you do that they cannot do s**t and you are fully and legally out of the German income tax system.
Also unless you have a specific requirement to do this funky HK business thing drop that and do the proper Maltese LTD + holding. You will get proper tax ids, certificates etc and can show that you are complying with European tax code, tax your profits at 35%, make full use of the double tax agreements e.g. while working for clients of your Maltese LTD during travel to Germany etc pp.
The Maltese LTD + holding depends on the CFC changes going live in 2019.
