PHP 7 Compatibility

Hi we are testing for PHP 7 compatibility and the plugin yields these errors:

FILE: /wp-content/plugins/gallery-by-supsystic/src/GridGallery/Optimization/Model/Encrypt.php
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FOUND 13 ERRORS AFFECTING 7 LINES
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14 | ERROR | Extension ‘mcrypt’ is deprecated since PHP 7.1 and removed since PHP 7.2; Use openssl (preferred) or pecl/mcrypt once available instead
14 | ERROR | Function mcrypt_get_iv_size() is deprecated since PHP 7.1 and removed since PHP 7.2; Use OpenSSL instead
15 | ERROR | Extension ‘mcrypt’ is deprecated since PHP 7.1 and removed since PHP 7.2; Use openssl (preferred) or pecl/mcrypt once available instead
15 | ERROR | Function mcrypt_create_iv() is deprecated since PHP 7.1 and removed since PHP 7.2; Use random_bytes() or OpenSSL instead
15 | ERROR | The constant “MCRYPT_RAND” is deprecated since PHP 7.1 and removed since PHP 7.2
16 | ERROR | Extension ‘mcrypt’ is deprecated since PHP 7.1 and removed since PHP 7.2; Use openssl (preferred) or pecl/mcrypt once available instead
16 | ERROR | Function mcrypt_encrypt() is deprecated since PHP 7.1 and removed since PHP 7.2; Use OpenSSL instead
29 | ERROR | Extension ‘mcrypt’ is deprecated since PHP 7.1 and removed since PHP 7.2; Use openssl (preferred) or pecl/mcrypt once available instead
29 | ERROR | Function mcrypt_get_iv_size() is deprecated since PHP 7.1 and removed since PHP 7.2; Use OpenSSL instead
35 | ERROR | Extension ‘mcrypt’ is deprecated since PHP 7.1 and removed since PHP 7.2; Use openssl (preferred) or pecl/mcrypt once available instead
35 | ERROR | Function mcrypt_decrypt() is deprecated since PHP 7.1 and removed since PHP 7.2; Use OpenSSL instead
45 | ERROR | The constant “MCRYPT_RIJNDAEL_128” is deprecated since PHP 7.1 and removed since PHP 7.2
48 | ERROR | The constant “MCRYPT_MODE_CBC” is deprecated since PHP 7.1 and removed since PHP 7.2
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FILE: /wp-content/plugins/gallery-by-supsystic/vendor/Twig/Lexer.php
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FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
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87 | WARNING | INI directive ‘mbstring.func_overload’ is deprecated since PHP 7.2
91 | WARNING | INI directive ‘mbstring.func_overload’ is deprecated since PHP 7.2
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FILE: /wp-content/plugins/gallery-by-supsystic/vendor/Twig/Compiler.php
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FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
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218 | WARNING | INI directive ‘mbstring.func_overload’ is deprecated since PHP 7.2
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Can you help address these?