Resolve "GET pictures from Backend to activity and snacks"

Closes #27

See merge request swp-unisport/team-warumkeinrust/user-frontend!33

Resolve "fix app.js according to new changes"

Closes #28

See merge request swp-unisport/team-warumkeinrust/user-frontend!32

Responsive design for all Pages and Devices

See merge request swp-unisport/team-warumkeinrust/user-frontend!29

Merge branch 'test-sizing-css-activ-wiss-question' of git.imp.fu-berlin.de:swp-unisport/team-warumkeinrust/user-frontend into test-sizing-css-activ-wiss-question

Merge branch 'master' of git.imp.fu-berlin.de:swp-unisport/team-warumkeinrust/user-frontend into test-sizing-css-activ-wiss-question

# Conflicts:
#   user-frontend/src/components/ActivityPage.js
#   user-frontend/src/components/QuestionPage.js
#   user-frontend/src/components/WissenssnackPage.js

Language-Button-Activated

Closes #24

See merge request swp-unisport/team-warumkeinrust/user-frontend!28

auf language-wechsel in welcome-screen verzichtet. daran wird schon in einem anderen Branch gearbeitet.

Add language de flag in Welcome page

Buttons wieder innerhalb jeder Komponente implementiert (wegen styling). Sprachenwechsel funktioniert. Fehlt noch in Welcome und Result. muss noch auf Backend-Änderungen gewartet.

Merge branch 'master' of https://git.imp.fu-berlin.de/swp-unisport/team-warumkeinrust/user-frontend into test-sizing-css-activ-wiss-question

- min-Tablet width bigger
- fix unisport-logo size in result screen

- Add col-xs, sm,md, lg in REsult screen
- Add lanscape media queries in activ-, wissen- & Question Page
- Small correction in Welcomscreen  for effect of center position

- Fit image size for all type of media and showing same size under any type of images

- Add Language Logo in Welcome Screen
- Delete Language Logo in wiss, aktiv, & question
- change all 5 Pages using simple Bootstrap4
- Delete not using CSS

changing language functions implemented. stills not working cause sending request each time the buttons get pressed leads to fetching data with different order.....which shows different content on the same page...

- Add responsive mobile Design of all mobile types
- Add New BG pic for desktop
- change Next button css

22 Fix css for all pages

Closes #22

See merge request swp-unisport/team-warumkeinrust/user-frontend!23

Merge branch 'master' of https://git.imp.fu-berlin.de/swp-unisport/team-warumkeinrust/user-frontend into 22-Fix-CSS-for-all-pages

Server communication

Closes #19

See merge request swp-unisport/team-warumkeinrust/user-frontend!19

Add new image pictures for test activ, wissenssnack, background