I often here German speakers using the present perfect for everything.
BUT, in English when an action is finished we use the past simple.
'I have worked a lot today. I am ready to go home now!' (today is not finished; this is correct)
Now it is evening and you are sitting over a drink with friends:
You say: 'Boy was today hard for me. I worked almost 10 hours!' (Your work day is finished. You worked hard)
CLICK HERE TO PRACTICE 2