I have never played this game, so will be of no further help. But here are some ideas to get you started.
Based on your problem & the hints given in related games:
0. Spreading this game properly will likely not be easy (assuming it's possible). If that matters, stop now.
1. Your first step should be:
Try to edit your game's resolution, in a cfg file (& if resolution edit doesn't stick in-game, try making cfg read-only).
SH5 hints that this file may be in subfolder under Documents, but it could be elsewhere (e.g. path-to-game).
If you get this to work, it may well not be a complete solution (some vert- views or something else like that).
2. Other promising ideas:
- There is a modding tool that works with SH5 & may fix specific problem views (S3D, aka Silent 3ditor)
- The DX9 tool available from from SH3 entry could also be attempted:
http://www.wsgf.org/dr/silent-hunter-iii3. Backup ideas (failing all else):
- windowed game, spread to borderless with ShiftWindow (or WinShift). May require cfg resolution edit.
- SoftTH fullscreen (adding 2 files, likely beside game's exe).
- registry (unlikely. search for part of game-name in keys to see if aspect/resolution values exist)
- HxD (hex edit, hard. Looking for aspect &/or resolution to edit, in hex)