I am trying to do some researches on the medicinal chemistry topic, but unfortunately the SciFinder was bolcked in my country (in this moment). Is there any platform like SciFinder for searching papers and chemical structures?
Yes, Some sites have been there like Library Genesis, also research gate. Some groups are made for searching and downloading paper on requested. You should participate in this research group Whereas you can download the paper. You can try also other servers of SciHub like Sci-Hub: removing barriers in the way of science. This site provides 3 to 4 servers, you can change acc to availability of paper.
For the Chemical structures database, lots of databases are available like Zincdatabase, ChEMBL, molmoll, Enamine, Chemaxon, Alinda, Zelinsky Institute, BCH research, Selena Chemicals, and others. You can try these platforms for downloading the chemical structure database.
If you have previously had access to SciFinder from another country eg. from a university in Germany, you can do a PROXY or VPN configuration on your PC in order to have remote access through the university IP address. Nevertheless, here you have a link with alternatives for chemical structure searching on the web.
Reaxys and Scifinder are both very good, some better suitable for certain tasks, but both are considered to be the only serious tools available for accessing the wealth of information in chemistry. Unfortunately, none of them is free, unless your university of company has a subscription to these services.