How do you guys memorise vocabulary?

I’ve just started trying to learn in Portuguese about a week ago. I am fluent in Spanish if it makes any difference. But I am struggling to memorise vocabulary currently. I am only using Duolingo and I have a one hour lesson with a teacher a week.

I feel like when I use Duolingo and I see the words, I know what they mean and everything, but as soon as I get off the app, I don’t remember them

Also, I keep finding myself accidentally saying Spanish words when trying to speak Portuguese

So any suggestions to memorise vocabulary would be really appreciated