"Internal Server Error" when I checkout!

Hi, at first, sorry for my bad english skills.

My Website is: muehlbastei-bautzen.de

Installed Plugins: AWE Booking, Hide-Title, Woocommerce, Contacform

Everytime I try to checkout I get the error “Internal Server Error§
You can try it on your own, when you try to book one of my rooms (don’t worry, you can do it, our business is under constructin)

Test-Booking here: http://www.muehlbastei-bautzen.de/apb-room-type/klein/

Woocommerce Report:

### WordPress Environment ###

Home URL: http://www.muehlbastei-bautzen.de
Site URL: http://www.muehlbastei-bautzen.de
WC Version: 2.6.2
Log Directory Writable: ✔
WP Version: 4.5.3
WP Multisite: –
WP Memory Limit: 256 MB
WP Debug Mode: –
WP Cron: ✔
Language: de_DE

### Server Environment ###

Server Info: Apache
PHP Version: 5.6.23-nmm1
PHP Post Max Size: 200 MB
PHP Time Limit: 30
PHP Max Input Vars: 10000
cURL Version: 7.35.0
OpenSSL/1.0.1f

SUHOSIN Installed: –
Max Upload Size: 200 MB
Default Timezone is UTC: ✔
fsockopen/cURL: ✔
SoapClient: ✔
DOMDocument: ✔
GZip: ✔
Multibyte String: ✔
Remote Post: ✔
Remote Get: ✔

### Database ###

WC Database Version: 2.6.2
:
woocommerce_sessions: ✔
woocommerce_api_keys: ✔
woocommerce_attribute_taxonomies: ✔
woocommerce_downloadable_product_permissions: ✔
woocommerce_order_items: ✔
woocommerce_order_itemmeta: ✔
woocommerce_tax_rates: ✔
woocommerce_tax_rate_locations: ✔
woocommerce_shipping_zones: ✔
woocommerce_shipping_zone_locations: ✔
woocommerce_shipping_zone_methods: ✔
woocommerce_payment_tokens: ✔
woocommerce_payment_tokenmeta: ✔
MaxMind GeoIP Database: ❌ Die GeoIP-Datenbank von MaxMind existiert nicht – die Lokalisierung wird nicht funktionieren. Du kannst sie von http://dev.maxmind.com/geoip/legacy/geolite/ herunterterladen und dann manuell in diesen Pfad kopieren:

### Active Plugins (8) ###

AweBooking: von AweTeam – 2.5.1
Hide Title: von Brandon Kraft & Randall Runnels – 1.0.4
SI CAPTCHA Anti-Spam: von Mike Challis – 2.7.7.7
Page Builder by SiteOrigin: von SiteOrigin – 2.4.10
SiteOrigin Widgets Bundle: von SiteOrigin – 1.6.2
Sydney Toolbox: von aThemes – 1.01
WooCommerce: von WooThemes – 2.6.2
WordPress Importer: von wordpressdotorg – 0.6.1

### Settings ###

Force SSL: –
Currency: EUR (€)
Currency Position: right_space
Thousand Separator: .
Decimal Separator: ,
Number of Decimals: 2

### API ###

API Enabled: ✔

### WC Pages ###

Shop-Basis: #64 - /shop/
Warenkorb: #65 - /warenkorb/
Kasse: #66 - /kasse/
Mein Konto: #67 - /mein-konto/

### Taxonomies ###

Product Types: external (external)
grouped (grouped)
simple (simple)
variable (variable)

### Theme ###

Name: Bistro
Version: 1.0
Author URL: http://athemes.com
Child Theme: ✔
Parent Theme Name: Sydney
Parent Theme Version: 1.30
Parent Theme Author URL: http://athemes.com
WooCommerce Support: ❌ Nicht angegeben

### Templates ###

Overrides: –

https://wordpress.org/plugins/woocommerce/