Note that the TDF builds downloaded from the LO site should install under /opt/ (unless you use the install script and override office-installation-dir) and not replace distribution files. You may have some fragments lingering around from an older installation (but even if you had 7.6.1 installed the 7.6.0 package message doesn’t make sense), and if you install the Help package you need the exact package matching the version, as offered during the download. Maybe you have a wrong package there, or forgot you had help installed with 7.6.0? Try to uninstall libobasis7.6-en-US-help-7.6.0.3-3.x86_64
If not and you are not trying to install versions in parallel I’d recommend to first uninstall / remove older versions that are not part of your distribution to start from scratch, as you now somehow seem to have created some mess.