The graph above depicts that

the german economy steadily improved up until 1923
paper marks became a substitute for gold marks by 1923
german paper marks rapidly lost value between 1918 and 1923
by 1923, the gold standard was used by most nations

German paper marks rapidly lost value between 1918 and 1923

Explanation:

Between the period 1918 ans 1923, the German economy crumbled rapidly and it had enormous inflation, resulting in large scale poverty in the country. This can be seen very well from the presented graph, as at 1918 one paper Mark was almost equivalent to one gold Mark. Then as the years pass by the paper Mark starts to lose on value, and by 1921 it is almost 1,000 paper Marks that were the equivalent of one golden Mark. From 1922 we have a sharp loss of value of the paper Mark continuing in the next 1923, with the end result being one billion paper Marks to be equivalent to one gold Mark.

less available tax revenue

this basically means that when they get money from taxes wirth having a lower gdp they get less then what others have with a higher gdp