Permission denied in Civi\Core\AssetBuilder->build()
This suggests a file permission issue on the relevant folder - which is sites/default/files/civicrm/persist/contribute/dyn/.

First, ensure the parent folders exist - both sites/default/files/civicrm/persist/contribute/dyn/ and sites/default/files/civicrm/persist/contribute/.  If both exist, check the permission AND owner of the dyn folder.  Is the owner the same user as the webserver user?  Likewise, if dyn doesn't exist do the same for contribute.  If you're not sure how to check owner/permissions, or how to interpret them, please either a) hop on https://chat.civicrm.org, or b) update the question with your operating system (including the distribution, if Linux) and webserver software (most likely Apache or nginx).