I mean i may place information in a place i really know but is it possible to forget the whole thing or forget what is that place i used for?
not if you do a spaced repetition.
As Erol says, without repetition/review any data in your palace will tend to fade. Which isn’t necessarily a bad thing if you only need to use that memorised information for a short period of time-say until you’ve passed whatever test.
Let me also mention that, because you are not using these methods for competing, you have all the time in the world to make stronger connections with your memory palace.
Let’s say you are in your kitchen and the locus is the Sink & Tap-Water area, and you want to remember a chemistry formula, you’d convert the data into an animated image based on what the info is, and then have them having a shower under the Sink-Tap. This way you are interacting the item at your location with the data you are memorising. And you visit that Sink area, it will just pop up at you and you should be able to recall it.
While you are creating the images, see if you can find a shape for the info you are trying to memorise. Let’s say, it’s a Triangle with A, B, C on each point, you’d then ask the question of what shape of an object in a real world looks like the triangle?
I’d immediately choose a Pyramid, and for the ABC, I might either use Acronym, or Letter Shapes to make a mini-story-link on each point. It could be “Apple, Banana, Carrot” and then have each of those fruits/Veg link to what it really means in the Chemistry and link them together again with a mini story action-link.