As a general remark, welcome into the jungle of authorship, patent ownership, and so on. Stealing intellectual property is extremely common, much more within companies than among competitors. Lab or group leaders do it very often, that's the basic reason why some "researchers" have so many publications. It may be hard to admit, but scientists are dishonest, chiefs more so.
Then, when several persons cooperate in a creation, each one honestly feels to be the main contributor. It's impossible to make a honest opinion about that.
One should also understand that many people get the same idea independently at the same time, just because the idea was ripe. Obvious cause of angriness, especially if these people discussed before. Take the electric car as an example: once lithium batteries existed, the electric car became usable, so dozens of companies and thousands of individual "invented" it.
I spend much time making inventions that I put on Internet forums freely available to anyone, and guess what, it's a rare exception when someone developing my ideas cites me, even when there is nothing to sell, like the mundane explanation of neutrinos faster than light or the goal of a Neanderthal construction. For industrial items like OLED or future fridges, relying on good faith would be foolish.
In that light, it is healthy practice to create proofs of everything you discover or invent, even before speaking with your colleagues. The proof must bear a date provided by someone else and be impossible to tamper, so a judge can decide you are the author. It won't ease the anger of your colleague who had his idea before you, but it avoids your anger as you date-stamped your idea first.
If you trust the internal email enough (...did you understand: I wouldn't?) to send your ideas to your colleagues through it, send yourself a copy too and save it including the header that contains information about the sender, recipient, date, hash and so on. "A copy" means: not in the company that will throw you away. But then, the information is outside the company, possibly vulnerable to competitors, so better encrypt it.
Better, send yourself emails (from and to home) where you append encrypted versions of your text. Choose the encryption properly.
You might send yourself letters with your ideas, but then encryption is difficult. Carbon paper adds on the text sheet the address you write on the envelope, but it gets rare. Affix the stamp on the opening.
At least in France, you can send an "enveloppe Soleau" to the patent officehttps://en.wikipedia.org/wiki/Soleau_envelopehttps://www.inpi.fr/fr/proteger-vos-creations/lenveloppe-soleau/enveloppe-soleauhttps://www.inpi.fr/fr/enveloppe-soleau
if the employer wants to protect an invention if France too, it works. Whether this exists elsewhere?
If you write notebooks with your experiments, ideas, computations, keep them with care. Exfiltrate them on time from your employer: the day your access badge doesn't open the door any more and a colleague brings you a careful selection of your belongings, it's too late. Judges may consider your notebooks as a proof despite you wrote them by yourself without an independent timestamp.
Laws about patents vary much. Whether inventions pertain to the employer depends on the country, the position (engineers may have a "creative role"), the contract, the field of the invention...
For instance in the US, an all-important target for patents, only the inventors can file a patent, not the employer. Better: citing a wrong inventor, including within the same team, is a cause to nullify a patent. This is one good means for an inventor to obtain his rights.
So if you have credible means (not destroyed by the checking!) to tell your boss and colleagues "I have proofs that I'm the inventor, put me in first position or the patent is null" your chances are excellent. If not, they are doubtful.
Welcome to Germany! Good choice for science and technology. In case you believed the legend of honest Germans, no: they're just normal.