How to straighten this part?

[leliep 28]

Hi Guys, what can I do to improve the corners of the part in the picture? I already tried reducing the speed from 70 mm/s to 30 mm/s, but no change.

It is being printed on my UM3 with two 0.4 nozzles and PLA. Slicing done with Cura 4.7.1
 

Thanks for any advice, -pl

 

[leliep 28]

To answer my own question: with a Print Speed of 70 mm/s and a Wall Speed of 24 mm/s for both hotends the corner parts of this model became straight as they should be.