To be honest, you have accent not just in some combination of letters, but in every combination and in every word. In my opinion it’s not something to be concerned about, because what you say is understandable. The only way to reduce accent is to live in Russian speaking country or community of Russian speakers in some other countries. But even then it may take years.

You really pronounce it well, you have a slight accent but it's nothing fatal, I'm sure any Russian can understand you without any problem. Just keep practising and speaking a lot and also read the texts in Russian out loud and your accent will completely disappear in no time.