python: one kernel density plot which includes multiple columns in a single dataframe
I did find how to work around by transforming the dataframe's columns into one single column. 

df.stack()
I need to make a single gaussian kernel density plot of a dataframe with multiple columns which includes all columns of the dataframe. Does anyone know how to do this?
So far I only found how to draw a gaussian kernel plot of a single column with seaborn. ax = sns.kdeplot(df['shop1'])
However, neither ax = sns.kdeplot(df)norax = sns.kdeplot(df['shop1','shop2]) do not work. 
Otherwise is there a workaround where I could transform the dataframe with shape df.shape(544, 33) to (17952, 2), by appending each columns to eachother?
The dataframe includes normalized prices for one product, whereas each column represents a different seller and the rows indicate date and time of the prices.