Well, thank you all for your replies and advises.
How I measure my progress? Very simple (but obviously wrong) way. I've learnt two languages on my own - what means I had kind of lessons (just that those lessons consisted with books and audio) - German and Italian and after 3 months I could use what I've learnt prety much (almost 100 %). OK, the truth is I was quite some younger (about 15 years younger) and (obviously) I could remember much more then I do now. That's why I've said that Welsh is WAY harder language to learn then any other language I've learnt. I also compare progress from those two self-taught languages as the way of learning was something I could take on my own, deciding how speedy or slow my learning shoudl go (what means similar to SSiW way). The hardness upon myself was as strong as it's now - no more no less.
English doesn't count here as a measure as I've started to learn it already in primary school and learning one language through the era of 10 or even more years and then on only kind of upgrading it, having many ways and abilities to practice the language almost on every corner should give some kind of results. So varities of how to say something in English really came kind of naturally and I don't even translate anything into Slovene anymore. I (now for example) just sit and type (quite fast that's why so many character mixtures) what I want to say just like I'd type in Slovene or Croatian language (and even in Croatian I'd think a bit how to write down something). So, yes, English really can't count into comparison how I measured the progress when learning it.
I will make no excuses on any thing. I actually don't strive to any particular goal but that one of comprehanding the things beign taught in lessons and being able to produce something out of what I've learnt in reasonable (rather shorter then longer) time.. Repeating one lesson twice or three times should be prety enough to remember things, putting sentences together or so. However there are times (quite many times) when I say or write something and all of a sudden I feel everything is way wrong especially with so many variations of Welsh language as I'm encountering in the process of learning right now.
But here is one excuse, which is sadly reasonable. I might never be able to go to one bootcamp due to financial reasons, not living in UK, so I might never have the real chance of speaking only Welsh for a day what even for a week (To make thigs clear, moaningn is not my intention here. I'm just saying the fact).
Tweets in Welsh @aran could very easily be cheating (what I normally don't do though except when needing to find new word I don't know yet) and to be honest with some of them I needed to use Google translate quite some times to be able to remember how to write down things (I always have written them dwon on my own and never did copy-paste though). My tweets you could see on my timeline though are as same as a parrot would write them down and as few as one could imagine what equals (almost) to none. More I am not able to do so that's why I don't count them as acheavement (I mean my tewwts not those of someone else).
And lesson 23 done almost 99 % I didn't say with how many repetitions of it I managed to get so high percentage. I believe I've repeated it for a week or so to be able to remember things and use them correctly (not to mention that I went through the whole Course 1 once before however with much higher tempo then the last time what was really wrong to do).
So, if I make kind of conclusion ...
Maybe I'd rather try to go through Level 1 and forget Course 1 completely except in things they're the same in both, then give myself a break of a month or even more (what was also suggested as an option here) because if I do a break of more then a week I'd surely loose everything what I've learnt so far (I did a break for 14 days once and came into real trouble getting back on track afterwards).
Diolch i bawb.