What engine are you using?
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Try deleting any unnecessary files and photos. If that doesn't work then go to finder or file explorer and right click on the uproject file and press compress file and then press the settings button at the top next to the blueprints button and then go to engine scalability and put everything to low and on the bottom of it there should be material quality level and put that to low and that should help. If it does please let me know. :)