How to fix Error: laravel.log could not be opened?

Never set a directory to 777. you should change directory ownership. so set your current user that you are logged in with as owner and the webserver user (www-data, apache, ...) as group. You can try this:

sudo chown -R {your current user}:www-data storage
sudo chown -R {your current user}:www-data bootstrap/cache

then to set directory permission try this:

chmod -R 775 storage
chmod -R 775 bootstrap/cache

Update:

Webserver user and group depends on your webserver and your OS. to figure out what's your web server user and group use the following commands. for nginx use:

ps aux|grep nginx|grep -v grep

for apache use:

ps aux | egrep '(apache|httpd)'