Thank you so much for your feedback! I am still a beginner and I really appreciate it.
Today the airport was not really busy but there were a lot of pilots from EGLL (yes, I am not kidding) requesting pushback, landing etc. so It was really annoying for me. :D
So I did not check the position of B777 thinking that he was in a gate that he should taxi forward, and gave him the taxi clearance. This is my fault, I always think that people are doing their part of the job corectly (especially when I am busy :D), so I go ahead and give them the clearance. From now on, I will be more careful when giving clearances.
And really I had no idea that I could give a clearance for option without a new traffic instruction, thanks for teaching me.
I learned a lot from you, my door is always open if you want to make some touch and goes and teach me new things by giving feedback!
And here are some landing screenshots for you: