Hello Dtwfung and cornelm,
(Thanks Erkan TEKGÜR)
I just can run prestashop 1.7.7.0, this version gave me many problems, but I already have it running without problems.
Primero debes colocar manualmente la muestra de errores y apuntarlos y luego regresar a tu versión anterior con tu backup y trabajar en corregir esos errores con tu versión anterior. Luego actualizar prestashop y con esto debería correr tu versión sin problemas.
Cuando estes en tu versión atenrior ve a tu
BO Advanced Parameters\ Information
Levanta todas las observaciones de "List of changed files"
Error 1
1-Reinstaler the version before the backups.
Go to the Localization -> Localization tab from the International menu.
Choose United kingdom and chose only language and currency. The download package option should be yes, then I pressed the import button. Repeat this process with the United States and any additional languages you work with.
Update prestashop version 1.7.7.0 and repeat step 3
With this I solved this problem.
Error 2
On the contact page the form disappeared and I solved it by changing a line that calls the form in the contact.tpl file
I replaced those lines with this:
{block name='page_content'}
{widget name="contactform"}
{/block}
rute: \themes\your-theme\templates\contact.tpl
If you need more help you can show me the errors of Debug mode.
I speak better Spanish, hope you can understand me
Regards.