HandBrake

Hi, I'm new here and actually new in using Handbrake, so my problem will probably look stupid, but I need some help nonetheless.
Recently I tried it out when I needed to hardcode srt subs to my video and it worked perfectly, the only problem is, that the file size became bigger by a lot. My source video is a 3 hour film, that takes up a little more than 8 gigs, but subtitled video is bigger than 11 gigs. When choosing presets, I set the same resolution as my source video, changed the framerate to "same as source", decreased audio bitrate and did not tinker with any other settings. The codec and container were left the same (H.264 ; MP4).
So, my problem is this: I just need to hardcode subs and nothing else. The filesize of the source video is ok, I don't need to reduce it. What presets should I choose, so my video's quality and size remains the same, or as close to source's as possible, while hardcoding subs? My pc is not very powerful, so experimenting by myself takes a lot of time.
Thank you and sorry for my English.

Without a log, it is difficult to determine what is going on, but...

When you re-encode a file the way you describe, the video is uncompressed, the subtitles are draw on the appropriate frames, and the result is recompressed. The video has become more complex than it originally was, so the "same" compression level will generally mean a larger file.

Add to all of this the likelihood that the original video was more compressed than you think it was, depending on the source, and handbrake is going to try to faithfully encode the distortions from the original encoding.

Ok, tonight I will try to do the same thing with more powerful pc and I will paste the log here.

So, here is my activity log (don't know how to embed it properly):

https://pastebin.com/embed_iframe/aVc1Vf0R

Please, suggest something, so that the file size would not increase and the video quality would not drop. Thank You.