Here are some suggestions to make your sentences flow more naturally:
"I've been practicing piano often this week. Since last week, I’ve had some great opportunities to improve my piano playing."
"I’ve been practicing often" sounds more natural here, and "I’ve had some opportunities" fits better as it emphasizes ongoing opportunities.
"These opportunities motivate me a lot. I want to concentrate on my music and the way I think."
"Motivate me very much" is correct, but "motivate me a lot" sounds more conversational. "The way I think" is clearer than "my thinking way."
"However, I can’t concentrate for long periods, so I always start practicing piano in the mornings."
"I can’t concentrate for long periods" is a more natural way to say this. The word "so" flows better here than "therefore."
"By the way, I like watching German dramas every day, but today I chose a movie instead."
"Every day" is the correct spacing here, and "instead" is enough without adding "them."
"I felt satisfied that I could watch a movie without subtitles."
"I felt satisfied" is more natural in this context.