Speak to your hosts, but in my experience you will need
1) The Jagdshein for Visitors and get this you will demonstrate that you have an equivalent of their Jagd hunting examinations etc. An FAC is usually good enough, but also showing DSC1 and 2 is even better. You host is also vouching for you. This now has to be done ahead of you arriving, or certainly where I hunt.
2) You will need to pass the German hunting test. From memory its 3 shots a seated and rested position, 3 shots standing and 3 shots at a running target. The target is a boar and its from 50m. It's not that difficult, but will be if use a heavy moderator and are used to shooting of bipods, sticks etc. There are scoring rings on the target and you have to get over a certain score to pass. If you can keep all your shots inside a paper plate size then you will be fine.
3) Insurance - you need third party liability. BASC covers you for overseas trips, but I usually get local cover for c€20 for the week.
Provided you have the above you can hunt on your own provided you have the correct permissions etc. Usually this will mean being on a stand with clearly defined arcs of fire.
4) Currently to take your own rifle is easy enough with the European Firearms Pass which is freely issued by your local Firearms department. God alone knows what will happen post BREXIT - nobody has a clue, although it looks as if you will have to get a temporary import permit if you are coming from outside the EU.
When it comes to the actual hunts, spend time with your hosts before hand and get them to explain very carefully what you can and cannot shoot. Find some good pictures of male, female, old and young boar, fallow, roe and red deer - have these on your smart phone and these then avoid any language difficulties.
With boar - if it has a big arse and is towards the front of a group of pigs, its a mature female. DO NOT SHOOT these. Its their breeding stock, plus the old females in order.
If its big and hairy with big shoulders and on its own - it's a big old male - may have a big trophy fee. If its three or four together, then a mid sized keilers - depends on what your host tells you.
If its small, or middle sized - fill your boots.
