They are introduced in the "Aspect" unit; you may be able to see the tips and notes by following this link: https://www.duolingo.com/skill/kl/Aspect-suffixes/tips-and-notes .
To quote just one paragraph from there:
-lI' specifically implies that action is headed towards some defined goal or end, while -taH is neutral in this respect. (It neither implies nor denies an endpoint.)
If you want to survive in Klingon society, don't apologize! When you feel confident that you have mastered this course, you will want to look into the Replacement Proverbs which serve the purpose you are looking for in apologizing.
However, don't feel like I was upset in any way. I know that you are trying to take in a lot of information in a short period and will forget some of it from time to time. I also knew we had a good explanation already prepared and I didn't want to have to try to recreate it here, so I referred you back to it.
tera'ngan jIHtaH, I'm afraid, and will always be. I actually applaud how you are intentionally introducing some features that will come in later lessons with a little mention in the Tips and Notes. Where that occurs in the other programs, it is often a mistake by the designers, and the Tips and Notes often stop quite early in the course.
In previous examples, if I recall correctly, the suffix Daq meant not only "in" or "at" but also "to". So, it is not possible to say: tengchaHDaq Hop wIlengtaH or maybe tengchaH HopDaq wIlengtaH? And if we didn't use Hop in this sentence, and only wanted to say we are travelling to a space station? Wouldn't tengchaHDaq wIlengtaH be possible?
The suffix -Daq is used to mark the location where an action happens. It can also be placed on destinations whether or not the destination is the object of a "verb of motion". When a verb is the type that takes the destination as the object, it is perhaps better style to leave the -Daq off so that it is clear that it is a destination and not the location, but since the object is included in the prefix, it is usually not very confusing if the -Daq is placed on the destination. Still, without context, it can be difficult to determine if the sentence tengchaHDaq wIlengtaH means, "We are traveling to the space station," or, "We are traveling to it on the space station." tengchaH wIlengtaH can only mean "We are traveling to the space station," and so can often be a clearer sentence. Both versions are accepted as correct answers in reverse exercise for this sentence.
When adding noun suffixes to a noun+adjectival verb, some of them go on the noun itself and some of them go at the end of the noun phrase (thus appearing to be on the verb). The ones that effect the noun itself, like plurals, qualifiers, and possessives go on the noun itself. The ones that effect how the noun phrase acts in the sentence, go on the whole phrase. These noun suffixes are -Daq, -vo', -mo', -vaD, and -'e'. The Tips & Notes for each of those should indicate that already, but I'll check them all to make sure they do. Thus to add the optional -Daq to the sentence you have commented on, it would be, tengchaH HopDaq wIlengtaH
No. That would mean, "We are traveling on the space station." Since tengchaH is not the object of leng (as indicated by the lack of inclusion in the prefix and in fact there is no stated destination since that would still be indicated in the prefix), then the locative noun (i.e. the one marked with -Daq) must be the location where the traveling happens, rather than the destination of the traveling.
There is still some ambiguity, since it is not clear whether your are traveling from one place within the space station to another place within the space station or whether you are inside the space station while the entire space station travels from one place outside the space station to another place outside the space station.
The first two words together tengchaH Hop mean, "the remote space station" or "the distant space station", but don't fit as part of the sentence. The ma- prefix has a subject of "we", but indicates that there is no object. So "the distant space station" is not the subject or the object and is also not marked as the location. Even though you have not included a period between the parts, the lack of any indication of how they connect makes that Klingon wording interpret as, "The distant space station. We are progressing through our travels."
To get the meaning you were aiming for you're going to need a slightly more complicated Klingon structure. I would probably say it as, malengtaHvIS Hop tengchaH ("While we are traveling, the space station is far away.") There are some other variations that would work as well.