Hi @adilsonsantana, welcome to Thunkable! 
Remember to check out our Community Guidelines and How to ask Great Questions v2.0 posts for tips on getting the best support from the Community on your issues.
Are you receiving a specific error in when you are attempting to upload new assets into your project? Can you share a screenshot of what you’re seeing when you upload a new asset?
Keep in mind that there are guidelines for uploading individual assets but also restrictions on the total size of your project.
Individual projects have a size limit of 50mb due to size restrictions for apps in the Google Play or Apple App Store. I will link our docs below for some additional guidance on this.