Convert Subtitle

Hello!

I'm looking for a good software to convert the subtitle format. "Srt" in ". Sup" to (BluRay).
I want to add subtitle "Romanian" in BluRay, but the quality is lacking compared to the "English". Below I made ??2 pictures

Picture 1 - Quality that want to subtitle

Picture 2 - poor quality, I made a subtitle demux."Srt" with the program "tsMuxe" and out like in the picture. (

I tried some software for converting the from. SRT. Sup caliteatea of "styles" Good but were problems synchronizing subtitles and fps.

Help me please.

Thanks