Hi,
So there seems to be alot of misconceptions of how customs and parcels deliveries are being handled through country lines.
First of all, if you are using a courier or a postal serice, there is no "This person has experience" because sending packages through country lines is nothing but a gamble, PERIOD!
THE ONLY EXCEPTION is for syndicates, cartells and personal deliveries PERIOD!
As stated before, if you send a package between different countries you need to look up different classifications, all countries in Europe have them and they apply to, hardware, precursors, food, equipment etc. You can call customs to find out where to look and get a hold of this list.
If someone tells you that they know how to "stealth" package and guarantees you parcel to be delivered, they are lying, PERIOD!
There are too many details to go into, but just to put it in a very simplified example, here is one. Between the border of Germany / Poland the export from Poland into Germany in 2020 was $73,1 Billion!
Now take in consideration, according to customs control not even 0,1% of all exports / imports are checked, so for a small parcel or envelope being "caught" and randomly checked the chances are astronomical, but still plausible.
So, to round it up. You can send packages using couriers and postal services, but there is always a chance they will be checked, doesn't matter who sends them, there are no "experienced" package delivery services it's all random.
If you really want to be safe, there is NO BORDER CONTROL between Germany and Poland on Poland A6 > Germany 11 Highway and Poland 10 > Germany 104 highway
Best of luck