My frustration levels are so high- Spent an hour or so strengthening Imperfect Subjunctive day before yesterday and now back to zero ! - it is ridiculous- got 3 units to go but my tree is so decayed - don't think I can ever get on top of it - this is a very discouraging course - a couple of Basics have degilded - what gives !
Duolingo's skill decay algorithm is far from perfect, especially in the longer term. I've been on Duolingo for nearly five years and I've done enough German practices to hit level 25 without making any use of Immersion (back when there was Immersion to make us of). Nevertheless, almost my whole German tree is de-gilded, right down to Basics 1: evidently Duolingo thinks I still need some more practice on "Ich bin ein Mann" :). These days I don't pay any attention to it -- for actually learning German on Duolingo, I find it more useful to do courses from German to other languages.
It's a shame that it doesn't work better, but at some point you just have to start ignoring the skill decay and trust to your own judgement of what you need to practise.
This is Duolingo's spaced repetition approach at work. It shows you things you've learned at times that will most help them stick in your head. If you keep the tree gold, you'll find it works really well. Sometimes that means you don't make any progress through the tree for a while - that's fine.
Duolingo takes account of how long it takes you to answer the question, and it takes account of whether or not you "peek" - whether or not you hold the mouse over a word to see what it means. When you can answer the questions quickly and without peeking, the skills will decay more slowly.
After you've strengthened the skills a few times, they'll start decaying more slowly, and then you'll be able to get further through the tree.
I saw your tree, and I saw there that other 46 skills need practice as most of them are overdue.
Listen to me, David (actually "read me", but you get the idea); Give yourself a moment to practice by using the general "Strengthen Skills" feature, rather than keep opening lessons to later leave them unsupervised. It is practice that makes perfect, not gluttony. It's not a race, take your time.
Spent an hour or so strengthening Imperfect Subjunctive day before yesterday and now back to zero !
I do occasional targeted skill revisions like this, but in general I find it more effective to put in a single revision lesson on them on each of several consecutive days, until they are (near) gold. (That's more effective for me, I don't know whether it's more effecive for the algorithm too.) Then I move on and let them decay a bit more before I go back to them.
it is ridiculous- got 3 units to go but my tree is so decayed
I've been there. I think I got to the Subjunctive Present, and after that things went downhill. I had been keeping my tree mostly golden, and then it became too hard (required too much time) to do this and progress. By the time I was where you are, I probably had as few gold skills as you have.
Forget how decayed the tree is, keep on at whatever is a good pace for you, and complete the tree - this is what I did, with the additional note that most of the time I have tried to do twice as much revision as new material. (Well, a couple of verb skills near the end of the tree I powered through, going deliberately faster than my usual pace, no longer caring about full comprehension, because the exposure to them and some time was more important than trying to master them at the initial contact.)
Near the end of the tree, I'm fairly sure I let it decay more so as to be sure to get in new lessons nearly every day, then had infrequent days when I did revision instead.
Getting those last 3 units will be a relief.
After I got those last 3 units I needed a break.
For the later verb skills (particularly those dealing with mood, such as subjunctive), I think Duolingo as a language learning tool has a little room for improvement. For example, it's about here that I think the learner needs more context and more narrative continuity than Duolingo can currently give, which suggests that starting to try to read native material at about this point is a good idea, as it should include better context. (A good dictionary app integrated into your browser or reading device, or a good physical dictionary, is useful. Reading native material can be painfully slow, particularly if you try to read at the same level as you read in your native language, but, it does feel like an achievement to even read a paragraph.)
And the Italian tree packs a lot of such skills into a short space at the end of the tree. It is not the most enticing or encouraging moment on the course. But keep at it!
Then take it easy for a while. Revise skills in the middle of the tree perhaps. I think I had a period when I did only one revision lesson a day - which was the best thing after the wave of skills at the end of the Italian tree. Sometimes I revised a bunch of earlier skills in a day, sometimes I revised a skill from later in the tree, sometimes I go and try out other languages - but I keep on coming back to my Italian tree.
don't think I can ever get on top of it
It gets better trust me. My tree is now nearly all gold at the start, other than a handful of skills which aren't decayed enough for me to revise - which when I get round to it can be easily revised in a single sitting.
And I am slowly but surely working on getting the last 20 skills gold. (That might sound a lot, but really I devoted a lot of time to other projects instead, so this is a good number for me to have ahead of me.) And moreover having revised them all a couple of times already, I feel like I am on top of this, that I'm confident enough in the material to get them gold now without serious difficulty; at one time, I didn't feel this way - like you - but I'm there now (although by no means perfect), and I hope this is ultimately encouraging to you.