Renata, it's normal enough at his age to have a hard time getting them to sleep that little bit they need to get them through to BT.
At his age, with my LO2, she was in the sling or the buggy, and I didn't pay too much attention to how long she slept for, or, towards the end, if she slept at all. She got to the point of doing 10 mins and after that we stopped trying for it
With LO1, much more time to ourselves
, I lay down with him and let him feed and snuggle to sleep for a wee nap. And I got a rest too. That's a nice option if you have it.
It's very individual territory. I would try to stop worrying about the length of that nap for now, given his age you want him to start going towards not having it, yk?, and do what is easiest for you.
If he's waking happy and has energy for his activity, then 1hr 10 may be enough for him now. It could be that he has a 35 min sleep cycle. His naps are likely to lengthen when he drops to 2 naps, yes.