Hi!
If you were hit by Penguin, you were hit for external links. You must analyze all your backlinks, especially those that have the exact keyword you lost your position on as an anchor text. Make a list of all the external link that come from spammy looking websites, and try to remove them (you can either contact each webmaster or you can use the disavow tool in GWT).
You should check your Google Analytics report and compare organic traffic from today with organic traffic from 21 Mai. See what keywords were bringing most of your traffic and check if you still have the same position you had in Google before the update.
If you don't know what rankings you had before the update, you can use the search engine optimization report from Google Analytics or the queries report from Google Webmaster tool, like this: compare the average position you have today and the average position you had before the update. Before doing that, make sure you filter out all the data for images and mobile (you want your average position to include only web results).
If you are still unsure, there is one more check you can do: search your keyword on bing. If you have the same position on bing - or relatively similar to the position you had in Google - and you are not even in top 10 in Google, then it means you were penalized. For example you still rank with "motor trade insurance" in Bing.
Hope this helps and good luck!