Are you using ‘open level’?
If so, when the new level opens, your player is spawned again as the default player, ie, without weapon.
If you want to continue with a weapon, you need to use either the game instance or save game to enable you to keep a consistent feel to the game between levels.
Game instance:
Save game:
What should I do to prevent this from happening?..
before going to another level
after going to another level
What should I add in the blueprints to go to another level with my weapon
thank you very much you are the best !!! 
I saw some examples like the links you gave me, and I want to ask you if can i put two cast to my box collision?alt text
Not quite sure what you mean. Both those pictures look ok…
If you mean than you have to try and cast to two different classes after one OnBeginOverlap – just connect the second cast to the first cast’s Cast Failed pin.
sorry, This would be the example of my question
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two cast together, cast to game instance and cast to first person, would it work?
No, because the game instance didn’t overlap.
Cast to character to check it IS your character overlapping. If it is the get the game instance, which you then have to cast to YOUR game instance, otherwise you can use it 
( or whatever you’re trying to do with the game instance )
You are a genius, you helped me a lot, I learned some things with you, I will be applying learned it…Thank you very much for taking the time to answer my questions.
You’re welcome
thanks for answering now I saw your answer,I understand.something else learned thanks for answering
