mojoPortal's multi site hosting does NOT require you to install additional copies of mojoPortal files.
Your error indicates you have a web.config file under the folder sites, so you must have installed mojoPortal in the /en folder and in the /ta folder, but that is not how you setup folder based child sites.
So your additional (and uneeded) installations of mojoPortal below the root site are getting Web.config conflicts as mentioned in the developer FAQ
You "can" install multiple copies like that and you can mitigate the web.config issues as discussed in the FAQ, but that is using different installations for each site, the whole idea of mojoPortal's multi site support is you don't have to do that, you can run all the sites from the same installation.
I recommend read the documentation carefully
Hope it helps,