A software application that is relatively small in size, works quickly, and probably has a somewhat limited feature set could be referred to as lightweight. So more full-featured software that moves slower is, by contrast, heavy. But usually you don't hear that usage; "lightweight" is the more common term.
I think the best term is for you situation is simply laggy, which is the adjectival form of lag.
Windows is laggy compared to Linux.
Microsoft Word is a laggy program.
In English, rather than a verb derived from the noun, we just have "lag" as both a noun and a verb. In the software context, "to lag" simply means "to experience lag."
The lag in Call of Duty was so bad last night that I couldn't even walk in a straight line.
Call of Duty was lagging so hard last night that I couldn't even walk in a straight line.
Whether "laggy" really has the same specificity as тормоз in Russian is up for debate. Software can feel laggy because the code is poorly written or just because the machine's hardware isn't up to the task.
For example, Adobe Suite products on my five-year-old work computer take forever to start up, and opening new screens can cause a mini-freeze while they load. But on my home computer, the exact same programs open up right away and run very quickly. Is my home computer overcoming laggy software with superior specs, or is my work computer causing perfectly good software to lag because of bad specs? Perhaps a bit of both, but whatever the case, "laggy" doesn't really suggest a root cause one way or the other.
Also, note that lag may not have anything to do with the software at all.
For example, a clever user experience designer may trick users into thinking his software is faster by modifying a loading screen, when ultimately the software takes just as long to load.
Or, in the Call of Duty example above, if I'm playing online multiplayer, the lag I experience is really just ping that happens because one or more players has slow internet and/or is located geographically far away from other players or the game server. It has nothing to do with the game itself (other than the software used to match people up into a game initially).
Ultimately, laggy doesn't describe the software per se, but rather how the software feels to use.
тормозconsidered rude word in this context.