Probably you’ll just need to slow down on adding new grammar lessons, and stick to just focusing on doing the reviews, until they get back down to a manageable level.
Or, if it’s really bad, you can always “Remove From Reviews” on some of the harder grammar points, to get your review stack down.
I’d suggest starting slow and finding your pace that way, rather than starting with a bunch of new lessons all at once. (In other words, don’t add new lessons until you feel comfortable with your current review levels. It’s not quite like WK, where it is typical to add a certain # of lessons every day, to keep to a kind of ‘schedule’. It’s better only to add new lessons when you’re ready for taking on more.)
If you get your grammar pace down, but still want more reviews per day, you could try using the new Vocab feature, and add some extra vocab lessons. The vocab is much easier than the grammar, so it can act as like a ‘filler’ type of review, in between the usual grammar reviews. (By ‘filler’, I just mean it doesn’t take as much mental effort; I don’t mean that it’s useless or ‘fluff’. )
Info about Vocab feature here: Update: 2/17 - Decks & Vocab Beta