Russian verbs are pretty much complex as in any other Slavic language, they are just quite irregular. Slovak verbs follow the same system as Russian but have far less irregularities.
Does it have six cases and three genders? Are there different declensions for each?
Slovak has six cases, seventh is rarely used, three genders. The combination of these have couple of declensions. Russian has only three declensions. Slovak has 13: four for masculine, four for neutral and five for feminine.
What I wanted to point out is that for example for me it is easier to learn Latin than Italian, or Sanskrit than Hindi (and I tried all four).
Well, you only have to read the former, whereas the latter involve speaking as well.
And the spoken Latin and Sanskrit movements? There are organizations and groups who proote speaking of these languages and people do speak them. If you want to learn to speak them you can.
My point was that Sanskrit and Latin are fusional hence easier than their modern descendants which are analytic.
To me it is easier for a language to have cases. It is easier then to translate it into my own language, which speeds up the learning process.
Yes, of course - the closer to your native language the better. But how much does this help with an agglutinative language?
The main difference with agglutinative languages and fusional is the number of cases in declensions. There are couple of ways how to translate this, for example cases not present in a fusional language are translated with a preposition and an adequate case it goes with it. For example when translating Hungarian to Slovak: Superessive = na + Locative, Sublative = na + Accusative, Adessive = pri + Locative, Ablative = od + Genitive, etc.
I once actually tried creating an agglutinative Slavic conlang by turning those prepositions in suffixes.