It's the same for me. Too high notes and I have to go on falsetto (always a miss), too low and I can't control the pitch... I think I confortably not suck within 1 1/2 octaves, not more than that. I can only pass levels when I'm lucky enough to have many questions around my 'sweet' spot.

The voicegym would be nice...

I can definitely relate.

Furthermore I came to realise that singing and listening are two very different skills. I’m not to bad in determining the right interval by ear. But when I try to sing an interval I’m kind of lost. My voice is producing a wrong pitch and then I’m distracted by that and totally lost, although I thought that I had the right sound in my head.

Using intervals you already know is really helpful - they are great mnemonics. I couldn't for the life of me go down the scale in major steps when I started on Interval Barks, my brain instantly dropped to a minor 7th and I simply couldn't hear it, but singing Mary Had a Little Lamb gave me an instant portal to a major 7th (and 6th) - it's like magic. Have a look at this list: https://www.earmaster.com/products/free-tools/interval-song-chart-generator.html

This game needs a major adjustment, the way I see it - it shouldn't be limited by time. folks should have as much time as they need in order to imagine the interval in their head and produce it with their own voice which are two different and demanding skills,
Similar to the intervals and chords games which are NOT time based and thus not stressful.
Experienced masters of solfege will have easy time breezing through the levels but it's okay as they're already skilled and do not need this challenge, the way it is currently set the game is stressful and NOT beneficial for beginners.

For practise -
i suggest using an interval songs list such as the one Skye supplied here.

For managing with the game -
Until the game gets the necessary adjustment I recommend that you'll use an instrument to gauge the interval and help you with getting the right pitch

I had the same issue at the begining (i am now level 50). What helped me was to notice the intervals i had to struggle with and worked it on the piano (exactly like the game) but : working one intervall at a time exclusively and take all the time i need. It helps internalizing. I use the game as a confirmation of my internalisation. Don't leave it because once done it will improve a lot your ear thru the internalisation of the intervalls. I really think it's the most usefull game.

@Skye Auer have you checked out this tool yet?
https://www.tonegym.co/tool/item?id=interval-memorizer

@XIN ToneGym great find, super helpful!

@amit That is an awesome tool thanks! @jean-Francois no intention of quitting but I also can't keep doing the same thing. thanks for the tip.

@Amit Fortus Yes, it's very helpful, though not so much for training for Interval barks - I find that using the memories I already have, ie from songs I already know, is easier and more reliable than trying to memorise them without context... I wish it included intervals of more than an octave though! My brain doesn't like having to do the math for games that go into the second octave, though I suspect I have learned more for it. :)

@Skye Auer
We're working on an update for the Interval Barks game.

As for the memorizing tool- it is not common at all to use these large intervals in a main melody of a song... Do you have any examples of songs that showcase these intervals clearly?

To help me sing notes accurately I use a free online tuner called TunerNinja. It visually shows you how accurately you sing a note in real-time,allowing you to adjust accordingly.Hope this helps.