Look at the immigration forms you will be using and see what kinds of things will be easier to do now rather than later in Canada.
At the very least, get your police checks now from Germany and any other country where you have lived for more than 6 months. The medical might be cheaper where you are now than in Canada. You will have to prove your relationship is genuine, so think of things you could use for that. For example, letters or affidavits from friends and family stating they believe your relationship is genuine; copies of anything that proves you live together, such as bank account statements, utility bills, lease or mortgage, credit card bills, etc.