Currency in the Netherlands and Germany is the Euro.
You can complete a currency exchange at your bank or AAA before you leave, at kiosks in Europe, or at the airport. Most places also accept cards, but it is good to have some cash on you just in case. The kiosks are like ATMs, and they will change a fee for the exchange/withdrawal. If I were you I would check and see if the academy has any currency exchange services. Exchanging at the airport is the most expensive.
DO NOT LOSE YOUR PASSPORT. Keep it on your person at all times.
There are pickpockets EVERYWHERE. Do not carry a bag/satchel, keep your money/passport/phone in a front-shirt pocket under your coat. Pickpockets are amazing and will slice open bags and reach their hands in unbuttoned/loose/open pockets. I am not kidding about this, a girl I was traveling with had her passport stolen in Munich right from her purse and she had to go to the consulate and was there all day for two days. Keep track of your stuff.
Pickpockets can also get nasty/violent if you are alone. DO NOT travel alone, especially at night, in areas that are not well populated. Don't walk down any alleys, don't get in any unmarked cabs, don't enter/leave any bars by yourself.
Carry a German phrase book with you. Most people there speak English, but it may help you in a jam.
Download the Viber app on your phone. It allows you to call/text/FaceTime internationally for free when on WiFi. You can also use Facebook Messenger for this.
One of the things that will help you get around most is by taking one of the little cards from your hotel front desk with the hotel address on it before you go sightseeing. If you get lost/need to take a cab/Uber, you can show the card with the address to your driver and they will know where to take you. If the hotel/accommodations do not have a card, take a picture of the hotel or an identifiable location (restaurant, theater, attraction) near to your hotel and you can show them that, just know what city you are staying in.
Be aware of yourself and your behavior. German police are wary of Americans and will fuck you up if they think you are acting up.
Save yourself money and do not buy trinkets and "authentic" bullshit from any kiosks or pop-up shops or gift shops in the markets. It is all cheap bullshit that isn't worth anything. Save your money for meaningful purchases (ex: a beer stein, they are legit).
Do not buy any historical/medieval weapons and try to bring them back on the plane with you. It will be confiscated by TSA and you will be put on a watch list for years (this is not a joke, this happened to a guy I was traveling with).
Do not engage with the prostitutes in Amsterdam.
One more time, DO NOT LOSE YOUR PASSPORT. If you lose track of everything else you can still get home and replace all of it, but losing your passport will screw you royally.
The number for German emergency services (like our 911) is 112 and you can call toll free from any phone, including phone booths.
Make sure that you and Goki find a landmark and set it as a meeting point in the event you are separated.