Upgrading Drupal

Hello,

I'm upgrading a site from D7 to D8. 

When running the upgrade, about two thirds of the files fail to upgrade. The migrate messages shows the following: Cannot read from non-readable stream (http://example.com//sites/default/files/images/dutoit_n_thumb.jpg)

I thought the // in the URL might be the problem, that the base URL is misconfigured somewhere. But then why do the other third of the files copy fine?

Any help would be much appreciated

Hello,

I have just upgraded a Drupla 8.6.10 to a 8.7.1. However once this is done, the whole site does not work anymore, so I made a restore of the site.
So he returned in 8.6.10, but shows me that he is up to date in 8.7.1 (first problem).
The second is that once I want to run my update.php Error 500, ditto if I want to clear the cache.
So I have this error message right now in the logs:

Hi,

I'm using lighting 8.x-3.208, drupal core 8.6.16.

I want to upgrade drupal core to 8.7.1, how can I do that? Do I need to modify composer.json file?

Below is my composer.json file:

I have an issue after upgrade from 8.3 to 8.6.10.

i have a form contains 1 filed with 'managed_file' type when i choose the file and click submit button the file didn't upload on specified directory but i choosed the file and click on upload icon it upload correctly.

my form filed like this:

Dear,

I use maintenance mode  during update and similar tasks, As everyone does, I think.

I have writen a few lines of a text in my "Maintenance mode message "

I had thought, that this maintenance mode  message was shown to every visitor during all the duration of the maintenance mode .

Find below the protocol of the upgrade: