You can try go to Themes -> edit code -> Assets folder -> base.css find the class .grid and add the property justify-content: center;

Can you provide the store URL?

{{ 'section-contact-form.css' | asset_url | stylesheet_tag }}{%- style -%}.section-{{ section.id }}-padding {padding-top: {{ section.settings.padding_top | times: 0.75 | round: 0 }}px;padding-bottom: {{ section.settings.padding_bottom | times: 0.75 |...

You need to change the name attributes of the inputs and textarea - remove the translation and set it as the official documentation https://shopify.dev/docs/themes/customer-engagement/add-contact-form for example: <input name="contact[name]"/>       ...

Can you provide the code of you contact-form section?Go to Themes -> Edit Code -> Sections -> contact-form.liquid

According to the shopify documentation  you sould use {{ 'customer.first_name' }} - remove the 'account' and the 't' filter, because you can't translate the customer's name Liquid objects: customer (shopify.dev)

Can you provide the store URL?

Try removing the line 193