Magento – Magento admin-panel isn’t working

I wanted to try working with Magento, so I downloaded the Magento 2.1.5 Community version from the website and installed in on my localserver from XAmpp (php 7.0.15).
Magento installed successfully (after changing some small php things), but after I logged in the adminpanel the buttons (on the left) weren't working and some logo's weren't loaded. I tried different things but they all didn't help. (cleared the cache)

So I tried again to download Magento but this time Magento 2.0.15. Same problem. I even have tried to install both with php 5.6 but then the installation wasn't successful.

So my question is, why isn't it working? and can it be solved easily? (if so, how?)

This are the console errors, it may be usefull:

<i> 
require.js Failed to load resource: net::ERR_CONNECTION_RESET
mixins.js Failed to load resource: net::ERR_CONNECTION_RESET
http://127.0.0.1/magento2/pub/static/version1490356509/adminhtml/Magento/backend/en_US/extjs/resources/css/ytheme-magento.css Failed to load resource: net::ERR_CONNECTION_RESET
http://127.0.0.1/magento2/pub/static/version1490356509/adminhtml/Magento/backend/en_US/extjs/resources/css/ext-all.css Failed to load resource: net::ERR_CONNECTION_RESET
requirejs-config.js:58 Uncaught TypeError: require is not a function
    at requirejs-config.js:58
    at requirejs-config.js:63
    at requirejs-config.js:398
magento-icon.svg Failed to load resource: net::ERR_CONNECTION_RESET
(index):39Uncaught TypeError: require.config is not a function
    at (index):39
(index):87Uncaught TypeError: require is not a function
    at (index):87
(index):286Uncaught TypeError: require is not a function
    at (index):286
(index):418Uncaught TypeError: require is not a function
    at (index):418
(index):463Uncaught TypeError: require is not a function
    at (index):463
(index):504Uncaught TypeError: require is not a function
    at (index):504
(index):527Uncaught TypeError: require is not a function
    at (index):527
(index):550Uncaught TypeError: require is not a function
    at (index):550
opensans-700.woff2 Failed to load resource: the server responded with a status of 404 (Not Found)
opensans-600.woff2 Failed to load resource: the server responded with a status of 404 (Not Found)
opensans-400.woff2 Failed to load resource: net::ERR_CONNECTION_RESET
admin-icons.woff2 Failed to load resource: net::ERR_CONNECTION_RESET
opensans-600.woff Failed to load resource: net::ERR_CONNECTION_RESET
opensans-700.woff Failed to load resource: net::ERR_CONNECTION_RESET
opensans-400.woff Failed to load resource: net::ERR_CONNECTION_RESET
admin-icons.woff Failed to load resource: net::ERR_CONNECTION_RESET
opensans-600.ttf Failed to load resource: net::ERR_CONNECTION_RESET
opensans-700.ttf Failed to load resource: net::ERR_CONNECTION_RESET
opensans-400.ttf Failed to load resource: net::ERR_CONNECTION_RESET
admin-icons.ttf Failed to load resource: net::ERR_CONNECTION_RESET
ytheme-magento.css Failed to load resource: the server responded with a status of 404 (Not Found)
ext-all.css Failed to load resource: the server responded with a status of 404 (Not Found)
</i>