How to correctly add expression to transparent background like on this question ffmpeg drawtext filter - create transparent background with text for my case (where there are 3 lines in bottom right corner):
ffmpeg -i videoin.mp4 -vf "[in]drawtext=enable='between(t,2.5,6.5)':fontsize=50:fontcolor=White:fontfile='ariblk.ttf':text='textline1':x=min(4*(tw\+10)-(abs(4-2*(t-2.5)))*(tw+10)-tw\,10):y=h-th-130, drawtext=enable='between(t,2.5,6.5)':fontsize=50:fontcolor=White:fontfile='ariblk.ttf':text='textline2':x=min(4*(tw\+10)-(abs(4-2*(t-2.5)))*(tw+10)-tw\,10):y=h-th-75, drawtext=enable='between(t,2.5,6.5)':fontsize=50:fontcolor=White:fontfile='ariblk.ttf':text='textline3':x=min(4*(tw\+10)-(abs(4-2*(t-2.5)))*(tw+10)-tw\,10):y=h-th-20[out]" -codec:a copy videoout.mp4