Resized photos

Hello,

Some photos, not all, are automatically resized (for example from 603px × 461px to 1080px × 826px.

Please, how can I avoid this and ensure that these photos retain their initial size?

Examples :
https://www.bricabracadabra.fr/annonce/etui-pour-google-nexus-7-style-crayons/
https://www.bricabracadabra.fr/annonce/sac-a-dos-moto-furygan-urban-iii-noir-et-blanc/
https://www.bricabracadabra.fr/annonce/a-reparer-ordinateur-toshiba-satellite-l555-10r/

Thanks by advance for your help ??

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