If you’re using Elementor header (as per demo), kindly refer here instead. This is steps on changing the default theme header logo.

1- Go to Appearance – Header
2- Click Add Image and Select File to upload your own logo

Image size 400×400

3- Once uploaded, select and click Select and crop
4- Click Skip cropping if you do not need to crop the image to 800×200
5- Click Publish to update to your site