I live in Canada and try to buy online two day time train tickets from Berlin to Gliwice Poland For May 03 . I can’t purchase it online for some reason but I am not comfortable to travel to Europe without reservation on train and not having tickets purchased.. what should I do ?
Did you try bahn.de ? I was able to find a few (good) connections that you can buy directly, specifically if the connection only involves EC and IC trains and not local ones.
For example leaving at 9.37 in the morning takes about 7.5 hours and with a price starting at 40 Euros. The 12:37 was even less: only 30 Euros. You may have to create a Deutsche Bahn account to book this, but it's a free account.
In general you should have no problems buying this directly at the train station at the date of departure, trains almost never sell out completely and if worst comes to worst, you just take the next one: there are around 20 daily!
However, same day tickets are typically more expensive since you can't make use of the substantial early booking saver rates.